Apple Watch Ultra 4 vs Garmin Fenix 9: Which Suits a Triathlete?

The Apple Watch Ultra 4 starts at £749 in the UK and the Garmin Fenix 9 starts at £859.99, so the Garmin costs £110.99 more at the 47mm size. Both have bright AMOLED screens. The difference for a triathlete comes down to battery, sensor support and which phone you own.

Specs side by side

	Apple Watch Ultra 4	Garmin Fenix 9
UK price	From £749	£859.99 (43mm and 47mm), £949.99 (51mm)
Case sizes	49mm titanium (natural or black)	43mm, 47mm and 51mm
Everyday battery	Up to 50 hours, 84 hours in Low Power Mode	Up to 16 days in smartwatch mode (47mm)
Longest workout battery	25 hours Extended Workout, 45 hours Max Extended Workout	81 hours in max battery GPS mode (47mm)
Display brightness	Up to 3,000 nits	About 2,000 nits
Phone needed	iPhone only	iPhone or Android

Apple’s figures come from its UK newsroom and product page. The Garmin figures are the ones we used in our Fenix 9 vs Forerunner 970 comparison. Both companies’ battery numbers are manufacturer claims, and we have not tested either watch over a race distance.

Battery for long-course racing

IRONMAN gives athletes 17 hours to finish. Apple’s 25-hour Extended Workout figure covers that on paper, and the 45-hour Max Extended Workout figure leaves a wide margin. The Fenix 9’s 81 hours in max battery GPS mode is far beyond a race day, which matters more for multi-day events, ultra runs or a week of training between charges. Long-battery modes usually trade some tracking detail for runtime, so check what each one turns down before you use it on race day. Apple also says 15 minutes on the charger gives 18 hours of use.

Sensors and multisport

Apple’s Ultra 4 announcement lists no new swim or multisport features. The watch runs watchOS, which has had a Multisport workout type since watchOS 9. Apple Watch pairs Bluetooth sensors and has no ANT+ radio, while Garmin watches support both. If your power meter or heart rate strap is ANT+ only, that decides it. Check our heart rate monitor guide for straps that work over Bluetooth.

Health and recovery

The Ultra 4 has a new sensing system that combines optical and electrical heart sensors, measures heart rate variability more often and produces a daily Readiness score from 0 to 10. Garmin builds its recovery view around Training Readiness and Training Status, which are on the Fenix line and on cheaper watches such as the Forerunner 170.

Who should buy which

Buy the Ultra 4 if you use an iPhone, want one watch for daily life and training, and race distances up to an IRONMAN on 25 hours or less of workout battery.
Buy the Fenix 9 if you use Android, need ANT+ sensors, or want days of battery between charges.
Look at cheaper Garmins if multisport tracking is the priority. Our Forerunner 970 review covers a triathlon-focused option that costs less than the Fenix.

This comparison is based on manufacturer specifications and published reports. We have not worn the Ultra 4 ourselves. See our Fenix 9 vs Fenix 8 Pro comparison if you are deciding within the Garmin range.

Available now

Apple sells the Ultra 4 direct and we have no affiliate link for it. For a triathlon-focused Garmin that costs less than the Fenix 9, the Forerunner 970 is at Tredz.

Check price on Tredz: Garmin Forerunner 970

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