Apple Watch Series 9 vs. Ultra 2: Series 9 is the smartwatch for most people while Ultra 2 caters to users who want more

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The Apple Watch Series 9 and Ultra 2 are Apple's flagship smartwatches. While they share many similarities — the ability to track workouts, monitor sleep habits, and send call, text, and app notifications — some differences make one more suitable to some people than the other. 

For instance, those wanting a premium smartwatch experience in a sleek form factor should opt for the Series 9. Conversely, if multi-day battery life, advanced activity tracking, and a rugged, durable design are preferred, then the Ultra 2 is the better choice. 

Below is a comprehensive comparison of the Series 9 and the Ultra 2, two of the best Apple Watch models you can buy. We looked at how each compares based on design, smartwatch functionality, health and fitness tracking, and battery life. Although we didn't pick an overall winner, the Series 9 is the best for most people, while the Ultra 2 fills a niche. 

Check out our reviews of the Apple Watch Series 9 and Apple Watch Ultra 2 for more specific information.

Apple Watch Series 9 vs. Ultra 2: Specs

Apple Watch Series 9 vs. Ultra 2: Size, design, and hardware

The noticeable differences between the Series 9 and the Ultra 2 are the size and design. The Ultra 2 has a larger case size (49mm) than the Series 9 (available in either 41mm or 45mm), and it's taller, wider, and deeper. This gives the Ultra 2 a bulkier form factor.

Both models have a dial (Digital Crown) and a button on their right side. Though these work similarly on both watches, the buttons on the Ultra 2 are larger. The Ultra 2 also has an extra button on the left side called the Action Button which can be set up to control various apps such as the Workout app, the stopwatch, the flashlight, and the Shortcut app. For instance, clicking the Action Button once can bring up the Workout app, while subsequent presses can start or stop a workout. 

The Ultra 2 is a far more robust wearable than the Series 9. It features a titanium case that makes it more heavy-duty overall and able to handle knocks better. Its screen is made of sapphire crystal glass, which adds to its durability. 

For the Series 9, it's available in two case options: aluminum or stainless steel. The aluminum model starts at $399 and comes with a standard glass display. The stainless steel model, which starts at $699, is a more durable option, and comes with the same sapphire crystal display as the Ultra 2.  

Internally, the Series 9 and Ultra 2 use the same S9 chipset and sensors like heart rate monitor, accelerometer, gyro, and altimeter. The Ultra 2 also has additional sensors for measuring skin temperature, water temperature sensor, and water depth.

The Series 9 comes in pink, black, blue, silver, gold, gray, or red, while the Ultra 2 is available in titanium.

Apple Watch Series 9 vs. Ultra 2: Smartwatch features

The Series 9 and Ultra 2 run the WatchOS 10 operating system, so the user experience is more or less the same. WatchOS 10 introduced redesigned apps that use more of the watch's screen face and a new Smart Stack design that allows quick access to various customized widgets and apps. It also made the Control Center accessible by pressing the right-side button, which is the menu that shows data like battery life, cellular connectivity, and Airplane Mode.

Both watches also have the new Double Tap Gesture. This unique feature allows users to perform certain actions by double-tapping their index finger and thumb. For instance, a double-tap can start or stop a timer, snooze an alarm, or answer or hang up a phone call. This is native to only the Series 9 and Ultra 2.

They also share the same smartwatch functionality like text and app notifications, the ability to make and take phone calls, and access to a wide library of apps via the Apple App Store. Both can stream music via services like Spotify or Apple Music and have Apple Maps, Calendar, and Apple Pay integration.

Each is customizable with a variety of interchangeable bands, too. These consist of the best designer Apple Watch bands, the best leather Apple Watch bands, or the best metal Apple Watch bands.

Apple Watch Series 9 vs. Ultra 2: Health and fitness tracking

The health and fitness tracking capabilities of the Series 9 and Ultra 2 are largely similar, though the Ultra 2 offers a few more features that cater to more advanced activities. These include tracking for watersports like scuba diving and freediving, and expanded altitude and depth sensing. 

The Ultra 2 also has a more brilliant screen as it can reach a brightness of 3,000 nits. This is mostly useful in bright, sunny conditions, making it ideal for outdoors enthusiasts. The Series 9's maximum brightness is 2,000 nits, which is good enough for most environments. 

Both watches have standard health and fitness tracking tools and a highly accurate built-in GPS. They can track various activities, including walking, running, cycling, and yoga. They are also designed to monitor sleep habits and stress levels and can track ovulation cycles and skin temperatures.

It's worth noting that the blood oxygen sensing technology the Series 9 and Ultra 2 originally offered when they were released is no longer available due to a patent dispute, which forced Apple to remove the feature.

Apple Watch Series 9 vs. Ultra 2: Battery life

The difference in battery life between the Series 9 and Ultra 2 is significant enough to sway someone to purchase one over the other. While the Series 9 offers 18 hours, the Ultra 2 can last 36 hours, thanks to a bigger battery. This means you'll need to charge the Series 9 daily, while the Ultra 2 needs a recharge every other day.

Both watches offer a low-power mode, but it turns off several features, like the always-on display, heart rate measurements, and the Double Tap Gesture. However, it dramatically extends battery life: The Series 9 can last up to 36 hours in low-power mode and 72 hours for the Ultra 2.

Apple Watch Series 9 vs. Ultra 2: Price

The Apple Watch Series 9 starts at $399 for the 41mm model and $429 for the 45mm model, while the Ultra 2 retails for $799 for the only sizing option available, the 49mm model.

Both watches go on sale sometimes, though you likely won't find them for more than $50 or $100 off their normal price.

Which should you buy?

Deciding between the Series 9 or Ultra 2 ultimately depends on how you intend to use either watch. The Series 9 is the better option for those who don't need the bells and whistles of the Ultra 2 and instead just want a premium smartwatch in a smaller form factor. 

While the Ultra 2 has similar smartwatch functionality, its additional advanced features are great for more active users. These features include a brighter screen, twice the battery life, and tracking capability for scuba diving, freediving, and other watersports like wakeboarding. It also has a unique Action Button and a wider range of altitude and depth sensing.

Beyond those differences, both watches are extremely similar. They can send and receive text messages, take phone calls, get app notifications, and track various activities. Both also have the unique Double Tap Gesture and feature the fast new S9 processor chip. 

If you want a premium smartwatch and don't need the extra features native to the Ultra 2, then the Series 9 is your best bet. If you're an avid athlete who could benefit from extra battery life and advanced fitness tracking, opt for the Ultra 2.