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Apple Watch Series 6 vs. Fitbit Sense: Top smartwatches go head to head

We compare the flagship Apple and Fitbit smartwatches to help you decide between the two.

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The Apple Watch Series 6 and Fitbit Sense are the top smartwatches that can help keep an eye on your fitness levels and act as a phone alternative on your wrist. Both also have an electrocardiogram (ECG or EKG -- Apple uses ECG) app, track workouts, sleep and blood oxygen levels, but they're different in the way they go about doing these things. To help you decide which is right for you, I've compared them on everything from fitness tracking to battery life and overall performance.

If you have an Android phone, the Fitbit is your only option, but both work with iOS devices, making the decision trickier if you have an iPhone. After two weeks of wearing these watches, I can tell you that there is no one-size-fits-all option. If you want the best overall smartwatch, with seamless fitness tracking and safety features, get the $399 (£379, AU$599) Apple Watch. If you want the most robust sleep tracking, temperature sensor and the best battery life, get the $329 (£299, AU$499) Fitbit Sense. (Check out our roundup of the best Black Friday deals on smartwatches and fitness trackers for the most up-to-date prices.)

Lexy Savvides/CNET

The latest Apple Watch has a robust set of fitness tracking features, an FDA-cleared ECG, blood oxygen tracking and all the responsiveness you could want from a smartwatch. It's also the better option if you need built-in LTE to use your watch without your iPhone nearby. Read the Apple Watch review.

Lexy Savvides/CNET

The Fitbit Sense also offers an FDA-cleared ECG, strong sleep tracking, a temperature sensor and a stress tracking sensor. Unlike the Apple Watch, it also works with Android, has plenty of third-party watch faces to choose from, and offers the better battery life of the two watches. Read the Fitbit Sense review.

Both are comfortable to wear, with familiar designs

The Series 6 looks like every other Apple Watch that has come before it, with a square face available in two sizes (either 40 or 44mm) plus a digital crown and side button. The Sense looks like a higher-end Versa and comes in just one 40mm size with a stainless steel rim around the square face, but instead of a physical button, it has an indentation on the side that vibrates when pressed and can be used to control the screen. While the Fitbit is physically larger than the 40mm Apple Watch, the actual screen size is only a hair bigger than the Apple Watch because of the bezels. The Apple Watch also has bezels around the screen, although they're slimmer than those on the Sense.

Each watch has a color, always-on screen that's easy to see in broad daylight, although I found the Apple Watch takes the edge for overall brightness when glancing down at my wrist during an outdoor workout. 

The Sense has many more watch faces to choose from than the Apple Watch, including third-party ones. However, you can further customize some Apple Watch faces to include complications, which are similar to shortcuts: They can display information such as weather or calendar appointments at a glance. Both also have different colors and hardware finishes to choose from.

Straps on both are easy to swap in and out with quick release buttons and you can change up the look with a wide variety of bands including leather, woven and silicone options.

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Screenshot by Lexy Savvides/CNET

Fitbit has added sensors, but you may not need them

Each watch can scan for potential signs of a heart condition called atrial fibrillation or aFib with their ECG apps. Place your finger on the digital crown for 30 seconds on the Apple Watch, while you place your index and thumb on the opposite corners of the Fitbit Sense for the same amount of time to take a reading. 

You can share results from both with your doctor. See where the ECG is available around the world on the Apple Watch and on the Fitbit Sense. Each watch can also monitor for signs of high or low heart rate and notify you accordingly.

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ECG on the Fitbit Sense

Lexy Savvides/CNET

Both can also track SpO2, or blood oxygen saturation, while you sleep. Check levels in the Health app on your iPhone for the Apple Watch, or wait for the Fitbit to calculate your nightly average on the SpO2 watch-face about an hour after waking up. It's also displayed in the sleep section within the Fitbit app as a graph, but will only show variations throughout the night and not exact percentages. The Apple Watch also lets you take a spot check of SpO2 and takes background readings throughout the day -- the Fitbit doesn't have an on-demand reading. Neither one of these watches are intended to be used as medical devices and may not be as accurate as a traditional pulse oximeter which is what doctors use to measure SpO2. 

Fitbit's watch has two additional sensors that the Apple Watch lacks: a temperature sensor that measures variations in skin temperature throughout the night, and an EDA or electrodermal activity sensor that uses sweat to determine stress levels. Changes in baseline temperature (like what's monitored with the Sense) can indicate a number of different conditions like the onset of a fever or changes in menstrual cycle. 

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Screenshot by Lexy Savvides/CNET

But as interesting as having all this data is, stress detection on the Sense in particular seems more like a work in progress than a fully fledged health feature at the moment. To take a measurement you first place your palm over the watch face for 2 minutes while the EDA sensor analyzes sweat levels. The watch then uses this metric, along with sleep, activity and heart rate variability data to calculate a stress score that can give you insight into how your body responds to stress. The problem is the Sense doesn't give you any indication of what to do with a high or low stress management score, like getting more sleep or holding off on a strenuous workout. There are some guided meditations in the Fitbit app, but I'm not sure how effective they were at reducing my stress levels. 

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The daily Stress Management Score from the Fitbit Sense

Screenshot by Scott Stein/CNET

To access these guided meditations, as well as guided workouts, more nuanced health data sleep and temperature variations you will need to pay $10 a month for a Fitbit Premium account. Apple will soon roll out its $10 a month Fitness Plus service that offers workout classes to cast on your iPhone, iPad or Apple TV and sync directly to your Apple Watch.

Both also offer native sleep tracking, but the Fitbit Sense has a lot more data about your sleep than the Apple Watch. Premium subscribers can get a breakdown of their sleep stages -- like deep, REM and light -- breathing rate, SpO2 and temperature variations culminating in a sleep score in the morning. The Apple Watch focuses more on establishing a healthy bedtime routine and mostly looks at duration of sleep which shows periods of awake time during the night as well as heart rate and SpO2 data. 

The Apple Watch also has a fall detection feature that can call emergency services and contacts if you remain motionless after a hard fall. It also has noise level alerts, irregular heart rate alerts, VO2 max measurements and mobility metrics. And it's also the only one that you can potentially give to kids or elderly relatives to keep an eye on their daily health data with Family Setup.

Great fitness trackers, but HR is more accurate on the Apple Watch

Each watch has a range of different exercises that it can track, on top of general metrics like steps and calories. The Apple Watch has over 40 different workouts to choose from while Fitbit has over 20 available that cover all the main options. Both watches also automatically detect certain workouts including walks and runs, so you get credit for your effort even if you forget to start a workout manually. They're also water-resistant, allowing them to track swims.

Both have built-in GPS so you can track the route of your outdoor workouts without bringing your phone, but the Sense takes around 10 seconds to acquire a signal outdoors while the Apple Watch is within 1 to 2 seconds. I did a 4-kilometer outdoor run on both and the distance and route were pretty much the same when I compared the Sense and Apple Watch results on a map.

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The Sense can show you what heart rate zone you're in and encourage you to push harder (or back off).

Lexy Savvides/CNET

The Sense also shows you heart rate zones such as cardio, fat burn and peak, on the screen in real time. It can buzz as you enter different heart rate zones, which may be helpful if you're trying to train at a particular intensity. 

However, when I compared the heart rate tracking on the Apple Watch and Sense for an outdoor run against a chest strap, the standard for this type of metric during workouts, I noticed the Apple Watch kept up while the Sense often lagged behind by about 20 to 30 beats per minute. After around 10 to 15 minutes, the Sense caught up to the strap's readings.

After your workout, the watches break down your metrics in either the iPhone Fitness app (Apple Watch), or the Fitbit app (Sense). I love how clearly the Fitbit app presents your workout data, including splits and heart rate zones. The Apple Watch only gives you your range, splits and heart rate on a graph rather than breaking it down into zones.

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The Apple Watch has more smart features 

While the Fitbit focuses on health tracking, the Apple Watch is the better package if you also want a designated smartwatch. You'll get more third-party apps, much tighter integration with the iPhone and faster performance overall. On the Fitbit Sense, even minor tasks like changing watch faces or syncing apps can take 30 seconds or more to complete, whereas on the Apple Watch it's almost instantaneous.

Responding to notifications or text messages is easy on the Apple Watch: dictate, send a quick canned response, or scribble on the keyboard. You can also take calls from your wrist because the mic and speaker are decent quality. If you have an iPhone, the Sense won't let you respond to notifications, but if you're on Android you can either send a quick response or dictate a message. The same goes for phone calls -- only Android users can make or answer calls from their wrist with the Sense as long as it's in range of the phone. 

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Lexy Savvides/CNET

The Apple Watch is the only one that has an LTE option for $100 more than the Wi-Fi only model (it costs $499 in the US) to take calls and stay connected without your phone nearby.

Each has the option to use a voice assistant: Siri on the Apple Watch, or Alexa on the Fitbit Sense. Google Assistant support is coming at some stage on the Sense, although at the time of this review it hasn't been activated on my watch. Put simply, Siri can do a lot more on the Apple Watch than Alexa on the Sense, like start a workout, send a text message or start a timer. Alexa is limited in what it can do, and it's a lot slower, but it does let you control smart home devices if you have any. The Apple Watch also lets you control smart home devices with Siri.

Finally, you can't store your own music on the Fitbit Sense. Instead, you're limited to downloading music for offline listening from Deezer or Pandora with a premium subscription. The Apple Watch on the other hand lets you store your own music (it has 32GB of storage) or download music from Apple Music for offline listening with a subscription.

Battery life is a clear win for the Fitbit Sense

With notifications from your phone, sleep tracking and the always-on display active, I was able to get a day and change out of the 40mm Apple Watch Series 6. You'll need at least 30% battery remaining to track your sleep, so you'll probably need to charge this watch every day to keep it topped up, unless you turn off the always-on display which can extend the battery life to almost two days. 

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Óscar Gutiérrez/CNET

The Fitbit Sense lasts two full days with notifications, always-on display and sleep tracking and  can extend it to almost 5 full days by turning off the always-on display.

Each watch charges with a proprietary magnetic puck that snaps on to the back. The Apple Watch charger is forwards and backwards-compatible with earlier Apple Watches, while the Fitbit Sense charger is designed specifically for the watch (so you can't use earlier Fitbit chargers from the Versa, for example, with the Sense). Both charge to 100% in about an hour and a half. 

Which is the better smartwatch?

The Apple Watch is the stronger overall smartwatch that blends fitness tracking with an ECG and SpO2 sensor, but only if you have an iPhone. The Fitbit Sense has a lot to offer for Android users, specifically if you want an ECG, robust sleep tracking and are intrigued by stress and temperature tracking.

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.