Apple Watch Series 3 vs Series 4: What's the difference?

The Apple Watch is a regular in our ranking of the best smartwatches, and with good reason: It has a bright, customizable display, offline music playback, a built-in heart rate monitor, and a bevy of apps that take advantage of all its features. But which model should you go for? In this article, we compare the Apple Watch Series 3 vs Series 4 to help you decide. 

For an in-depth look at each model individually, see our Apple Watch Series 4 review or our Apple Watch Series 3 review. Alternatively, read on to see how the two match up in terms of price, display, colors, health and fitness, performance and battery life.

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Apple discontinued the Apple Watch Series 4, but still sells the Series 3 and the Series 5. The Series 4 is still available through some online retailers, but is only worth purchasing if it drops below $399. Be sure to check out our Apple Watch Series 5 review, as well as our Apple Watch Series 5 vs Apple Watch 3 comparison.

You may want to wait for the Apple Watch 6, too, due out in fall. 

Apple Watch Series 3 vs Series 4: Specs

Apple Watch Series 3 vs Series 4: Price

In the widgets below, you can see how the prices compare in your region right now (alternatively, be sure to check out our best Apple Watch deals page for the latest discounts).

Discounts and offers aside though, let's get it out of the way: the Series 4 is expensive. The smaller, 40mm model starts at $399 (£399/AU$599), or $499 (£499/AU$699) if you want cellular connectivity. Want a bigger size? That'll cost you extra: $429 (£429/AU$649) for the 44mm GPS model, or $529 (£529/AU$799) for the LTE version.

The Series 3 is downright affordable by comparison. The 38mm model starts at $199 for GPS and $299 with LTE. The 42mm version starts at $229 with GPS and $299 with cellular.

If your biggest concern is your wallet, the 38mm Series 3 without LTE is the way to go. It's also a great device, and in my experience, cellular connectivity isn't essential. 

Winner: Series 3

Apple Watch Series 3 vs Series 4: Display

The Series 4's expanded display is its most obvious selling point. Apple stripped away the bezels and brought the screen nearly to the edges on both models. The smaller, 40mm Series 4 has a 394 x 324 display, which is larger than the 312 x 290 panel on the 42mm Series 3, despite the Series 3's bigger case. The 44mm has an even more massive 368 x 448 OLED panel, which looks beautiful but is also great for accessibility.

The bigger display is an improvement in every way. Apple designed new watch faces to take advantage of the extra space. Some are dynamic with flames, vapor and water, others are packed with complications for quick access to your most-used watch apps. Everything is more detailed. The dynamic faces are also available on the Series 3, but they don't extend to the edges of the display. Instead, the flames and vapor are limited to the radius encircling the dial.

Pulling up a map of Manhattan on the 38mm Series 3 and the 40mm Series 4, I was blown away by how much larger and more detailed my location appeared on the bigger screen. The Series 3 now looks dated by comparison, and it's only a year old.

Winner: Series 4

Apple Watch Series 3 vs Series 4: Size

With a bigger display comes a slightly bigger case, which is a bummer for people who preferred the 38mm size.

I still prefer the smaller size, but I found the 40mm to be a decent fit for my small wrist. I wish the new watch were smaller, but I found it to be a small sacrifice for the bigger screen and the health potential in the Series 4.

The 38mm Series 3 is still available to buy, and with all the features packed in watchOS 5, you'll still feel like you have a cutting-edge smartwatch, even without a giant display.

Winner: Series 3

Apple Watch Series 3 vs Series 4: Colors

Apple is nudging you to buy a Series 4 purely for aesthetic reasons — the new watch comes in two finishes (stainless steel and aluminum) and three colors (silver, space gray or black and gold).

The Series 3 is available only in silver and space-gray aluminum these days, though you can still find last year's gold aluminum models at other retailers.

Winner: Series 4

Apple Watch Series 3 vs Series 4: Health and fitness

The Apple Watch was already a great swim-proof fitness tracker, but Apple doubled down on the watch's health potential with the Series 4. This smartwatch has an electrical heart-rate sensor, which, combined with an FDA-cleared ECG app, is capable of diagnosing atrial fibrillation. We compared the results to a full, 12-lead EKG in a hospital, and found them to be accurate (see how to use the Apple Watch ECG app for more on this). 

The Series 3 also received a heart health feature in the same update, an irregular heart rhythm tool that passively monitors your heartbeat in the background. Both features have been cleared by the FDA.

The Series 4 also has a next-generation accelerometer and gyroscope, which can detect motion and impact if you turn on the watch's new Fall Detection feature. If you remain motionless for a minute after falling, your watch will dial emergency services for you. This could be huge, especially for elderly watch wearers.

WatchOS 5 brought with it health features including Low Heart Rate alerts and a forthcoming irregular heart rhythm alert, as well as one-on-one activity challenges and automatic workout detection. WatchOS 6 added apps for tracking periods and measuring noise levels.

But the game-changing FDA-cleared atrial-fibrillation diagnosis is a sign of where Apple is taking its most personal device ever. If you're concerned about your health, the Series 4 is the watch to get.

Winner: Series 4

Apple Watch Series 3 vs Series 4: Performance

The Series 4 definitely has more zip than the Series 3, thanks to a new S4 chip. I opened the Maps app and selected Current Location on each watch simultaneously (both running the latest version of watchOS). The Series 3 lagged a few seconds behind the Series 4.

Siri is also faster on the Series 4, and easier to use now that you can just raise your wrist and start talking. On the Series 3, you have to press the Digital Crown or say, "Hey Siri" to activate the assistant.

Winner: Series 4

Apple Watch Series 3 vs Series 4: Battery life

One area where Apple's wearables continue to fall short compared with rival watches is battery life. Competing smartwatches from Fitbit and Samsung can easily last four days on a charge, even with daily workouts.

The Series 3 and Series 4 both last about 18 hours on a charge with mixed use, or a little more than a day if you don't work out. If you try to rely on a cellular connection and leave your phone at home, you'll be lucky if the watch lasts eight hours.

Winner: Draw

Apple Watch Series 3 vs Series 4: Bottom Line

The Series 3 wins on size and price, if those are your biggest concerns. With watchOS 5, the Series 3 gained great new fitness-tracking features. Irregular-heart-rhythm notifications, one of the FDA-cleared health features, came to all watches running watchOS 5, so the Series 3 is now a more capable health device, too.

But the Series 4 has more advanced sensors, a larger, easier-to-use display, and the potential to become even more powerful with software features that take advantage of both the size of the Series 4's screen and the data from the watch's sensors.

If you have cash to spare and the 40mm isn't too large for your wrist, splurge on the Series 4 — but only if its price is significantly lower than that of the Apple Watch Series 5.