Apple Watch Series 4: Both sizes, compared

Larger display, new heart-rate sensor, new watch faces: the Apple Watch Series 4 promises a whole lot that's new. (Seen here: the smaller 40mm version).

Some watch faces take more advantage of the larger display area and nice curved display edges, like the iPhone X. (Kaleidoscope watch face)

Both displays are bigger now, keeping case size still relatively compact. The 40mm (left) and 44mm (right), in stainless steel (gold colored steel is on the right).

The Earth-view Astronomy watch face is a classic. Seen here on the 44mm gold steel version.

The gold steel with gold band is...very gold.

The 40mm (left); the 44mm (right).

Lots of motion-active explodey-smoky watch faces have been added to WatchOS 5, and they look nice here.

Comparing Mickey on last year's 42mm Apple Watch S3 (left) and the 44mm Apple Watch S4 (right).

A good look at the squared-off display and bezel on the 42mm S3 in steel (left) vs. the rounded edges of the 44mm S4 in steel's display (right).

Apple Watch S4, 40mm (left), Apple Watch S3, 42mm (center), Apple Watch S4, 44mm (right). Notice how the Liquid Metal watch face looks different.

The older Apple Watches force some watch faces to be small circles, while the S4 gets to enjoy a full-screen graphic (42mm S3, left; 40mm S4, right)

The new Infograph Modular watch face on the S4 (40mm, left; 44mm, right)

The heart-rate sensor's totally new, and cellular reception promises to be better due to an all-ceramic back. (S3 42mm, left; S4 40mm, right)

The green LED sensor has a different glow now.

Another look at the heart-rate sensor. The S4 also adds electrocardiogram (EKG or ECG) for medical-grade heart-rate readings to check for possible arrhythmia, coming later this year.

This is the Pride watch face on the larger Apple Watch S4.

The original Modular watch face is still on Apple Watch Series 4, and it's definitely more minimal than Infograph.

Round watch faces look fuller now, thanks to the larger screen and minimal bezels.

The full-motion watch faces such as Liquid Metal can go full-screen or be shown in a smaller circle with added complications. But it's always with analog watch face hands.

Taking at look at gold from the side: the Series 4 has a louder, clearer speaker.

How gold is the gold? It's more bronze-ish, and it's growing on me -- but I still wouldn't get gold.

The Infograph watch face is one of two unique, exclusive Series 4 offerings. There are eight (!) complications and an analog face. Busy -- or beautiful?

The red band around the digital crown indicates that this model is LTE-equipped. 

The Siri watch face is back! It hooks into more suggestions with WatchOS 5.

The digital crown has haptics now, meaning you can feel subtle clicks as you turn it. Not needed, but a very nice sensation.

Coming to the Apple Watch Series 4 later this year is FDA-cleared ECG, via an embedded electrical heart-rate sensor that requires touching the crown for 30 seconds to complete the circuit. More testing on that in the future.

All the standard Apple Watch faces are back, but many look slightly larger, optimized for the new larger displays.

The side button is more flush with the watch's case now, by the way. 

New Apple Watch models work with older bands. 40mm and 38mm bands are compatible with one another; likewise for 44mm and 42mm bands.

The hypnotic Breathe watch face, new to WatchOS 5, launches the Breathe app and has a pulsing charm.

Wearing the watch around New York, the larger watch face is easier to read in general.

The larger watch case and slightly thinner case make the watch seem thinner overall.

The heart-rate monitor now can send alerts for abnormally low or high sedentary heart rate, and can detect arrhythmia.

If you have a Series 3, you probably don't need to upgrade but you may want to.

The classic Chronograph watch face on the 44mm gold steel watch.

Kaleidoscope's new patterns add more color schemes and some abstract looks.

Shiny.

Vapor watch face is totally mysterious, very David Lynch.

Read our review of the Apple Watch Series 4.