It was when I did an interval workout that I began to notice some flaws. Both devices recorded my heart rate each second. I then exported the data and analyzed it in an Excel spreadsheet. You can view it below.
As you can see, during my 12-minute warm up the heart rate information is similar between the two devices. The data remained consistent during my first interval and through my first rest cycle. Starting with the second interval, however, the Forerunner 235 struggled to keep pace with the chest strap. At the 21:30 mark, it measured my heart rate at 164, while the chest strap had me at 184.
This continued for subsequent intervals and rest cycles. It wasn't until a few minutes into my cooldown that the Forerunner 235 was able to close the gap. At the 50-minute mark, the watch measured my heart rate at 159 bpm compared to the chest strap's 166 bpm.
The problems I encountered could possibly be ironed out in a future software update. If you need up-to-the-second accurate heart rate data, there is the option to pair an ANT+ chest strap to the Forerunner 235. It should also be noted that the further the watch is from the wrist bone (about two finger lengths) the more accurate measurements will be.
The heart rate data recorded on the Forerunner 235 can also be shared to other ANT+ compatible devices, such as Garmin's Edge bike computers. It's a bit tricky to set up, though. You have to scroll down to the heart rate watch screen, then press and hold the up key, and select Broadcast Heart Rate.
Garmin's app still needs work
Garmin has been slowly improving its Connect mobile app on Android and iPhone. There's now personalized insights and feedback based on your daily activities. The app is better than it once was, but it's still not as good as what Fitbit and Jawbone offer.
Garmin simply tries to do too much with it. These devices can record a ton of data, but there are simply too many menus to browse through to find all of it. I've used Garmin devices more than anyone I know, and it even took me a couple of minutes to figure out how to disable or change certain features.
I've also experienced occasional hiccups with connectivity between the app and the watch. Sometimes the watch wouldn't sync my workouts until I opened the app, which was a little annoying. Other times the watch would disconnect from the app for a few minutes before reconnecting. It didn't happen very often, but app connectivity is still something Garmin needs to work on with all of its products.
The Forerunner 235 also supports third-party apps, watch faces and widgets...sort of. The Connect IQ store, which can be accessed from the Connect app, has been around for a year now, but it still lacks useful apps and widgets. There's potential here, but it doesn't seem like developers have jumped on board just yet.
Battery life is good
The Forerunner 235 will last you about 11 hours with an active GPS signal, an hour longer than the 225. That time drops to under 9 hours if you use both GPS and GLONASS. Garmin has said that in watch mode with notifications and heart rate enabled, the watch should last up to nine days. I generally charged it once a week, but your time will vary based on how much you run.
The best overall GPS running watch
If you're looking for a GPS running watch with heart rate, the Forerunner 235 is worth the investment. The heart rate measurements aren't perfect during hard workouts, but the benefits of the watch outweigh the cons by a mile. It's accurate at measuring pace and distance, provides easy-to-read smartphone alerts and has a ton of running features that are typically found on more advanced devices. Simply put: It's a great value.
If you aren't interested in heart rate, the Forerunner 230 is equally appealing. It has all the same features as the 235, but is $80 cheaper and doesn't have an optical heart-rate sensor. While the watch gets better battery life (16 hours with GPS, up to five weeks as a watch with notifications), certain features, such as the recovery advisor and VO2 Max estimates, will require a heart-rate chest strap to use.