Apple Watch Ultra 4 vs Apple Watch Ultra 3: what's changed, and should you upgrade?

Apple's September 9 'Surprise and Shine' event has come and gone, and we've learned a lot about Apple's latest crop of devices. While we've got new AirPods and iPhones (including Apple's first foldable, the iPhone Duo), it's the Apple Watches that have caught my eye as TechRadar's resident fitness and wearables writer — specifically, the Apple Watch Ultra 4, the latest version of Apple's flagship watch series.

But how does it compare to the previous gen, the Apple Watch Ultra 3 — and is it worth upgrading? Read on for a full comparison of both watches, so you can make an informed decision.

Apple Watch Ultra 4 vs Apple Watch Ultra 3: Specifications

Apple Watch Ultra 4 vs Apple Watch Ultra 3: Price and availability

• Price is unchanged from last year
• $799 / £749 / AU$1,399
• Available from September 18

Here's an easy one to start with: the Apple Watch Ultra 4's price is unchanged from last year, at $799 / £749 / AU$1,399. It's available from the September 18, so if you were considering getting an Apple Watch Ultra 3 but were holding out, there's no reason not to wait a few days for the latest model.

Apple Watch Ultra 4 vs Apple Watch Ultra 3: design

Physically, little has changed in terms of looks, but there have been subtle tweaks. The titanium case is still there, slightly wider and slimmer than last year, and it lasts six hours longer than the Ultra 3 to make it to two days, or 18 hours with continuous GPS use.

The watch's heart rate accuracy is even better thanks to the new Health Sensing System. This redesign of Apple's LED optical heart rate sensor tech offers better skin contact thanks to an increased electrode surface area. Heart rate readings are now being taken up to every five seconds, with heart rate variability, an overnight measure of rest and recovery, being read up to every five minutes.

This makes Apple's heart rate sensor the most accurate of any wearable, according to Apple. It has apparently conducted tests against rivals using ECG chest straps, much like we do in our reviews.

I can attest that the Apple Watch Ultra 3 is as accurate a wearable as it gets, so I'll be intrigued to test the new Ultra 4 against my trusty Polar H10.

Apple Watch Ultra 4 vs Apple Watch Ultra 3: Features

• Finally, a Readiness Score
• New Audio Intelligence features
• Redesigned Health app

At last! Apple Watch gets a Readiness Score, a feature almost every other fitness wearable has had for years. Typically from Apple, it looks like the bee's knees, feeding into Vitals to generate a holistic overview of your night, and updating throughout the day, like Garmin's Body Battery function. A new Health Age feature also compares your current fitness level to those in your age group, much like Garmin's Fitness Age or Whoop's, er, Whoop Age.

It's unclear at the moment whether the Ultra 3 will get these features, or if it will be an Ultra 4 / Series 12 exclusive. But all the Apple Watch Ultra 3 features, including LTE and satellite connectivity, are available on the Ultra 4.

An incoming redesigned Health app on iPhone is Apple Intelligence-forward, offering personalized AI-powered insights, and what is clear is that this will also work with the Apple Watch Ultra 3 and all Apple Intelligence-compatible iPhones. This Health App will show you Readiness, Longevity, and allow you to measure your VO2 Max using a coached guided workout on your iPhone's camera, then update it according to your activity levels and metrics.

Audio Intelligence features are exclusive to the Ultra 4 and Series 12, and include Shazam on your wrist, Sound Recognition (your watch will let you know the doorbell's rung or a siren's going off, for example), and two more features which are sure to prove controversial.

Live Rewind has your watch listen to and instantly recall a conversation up to 15 seconds previously, by double-tapping the crown of your Apple Watch. Siri Recap listens throughout the day and uses Siri AI to process live audio files, serving you a summary of the day in the evening. There are numerous controls and privacy safeguards in place here, but there's no doubt they'll come across as creepy to many. You can read all about Audio Intelligence on Apple Watch here.

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