The Apple Watch Ultra 3 and Garmin Fenix 8 Pro are two of the best sports watches available, and show how the gap between true smartwatches and dedicated sports devices has shrunk in recent years. Along with its outstanding sports features, the Fenix 8 Pro has smarts like music storage and NFC payments, and offers LTE and satellite connectivity as well.
Meanwhile, the Apple Watch Ultra 3 has the longest battery life in an Apple Watch yet, and its native sports tracking is now good enough to satisfy even serious athletes thanks to features like training load and its structured workout builder.
I’m a big fan of both watches and wanted to see how they handled a marathon, so I took them away for the Loch Ness Marathon to compare their GPS and heart rate accuracy, battery life and design. Neither helped me track down Nessie, but both impressed me on the trip. Here’s the overall winner based on my testing.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: price
The Apple Watch Ultra 3 comes in one size and two colors —- black or natural titanium — and costs $799.
It’s considerably cheaper than the Garmin Fenix 8 Pro, which costs $1199-1299 for the AMOLED model I’ve been testing. There’s also a MicroLED version of the watch, which will set you back $1999.
The Fenix 8 Pro AMOLED comes in two sizes —- 47mm and 51mm — and two colors — grey and black.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: Specs
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: design and comfort
These are both large watches made from durable materials, with titanium bezels and sapphire crystal screens. They are built to withstand the elements even if you’re planning to head into the wilderness for days, and so are certainly tough enough to handle a marathon where it didn’t even rain much (for Scotland).
The rugged, chunky designs do mean that they feel quite heavy on the wrist though, especially the Fenix 8 Pro, which sticks out more because it’s thicker than the Apple Watch.
As someone with thin wrists, I prefer the slightly sleeker look and feel of the Ultra, and it’s more comfortable to sleep with, but the Fenix 8 Pro has a couple of advantages in its design.
One is the built-in flashlight, which is very handy and better than the torch mode on the Ultra 3. The other is the fact it has five buttons compared to three on the Ultra 3, which makes it easier to navigate the Fenix 8 Pro’s menus and use the watch during workouts without having to use the touchscreen.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: GPS & heart rate accuracy
I had both watches in their most accurate GPS mode for the marathon, which uses dual-band GPS with both, and checked the GPS tracks after the race using the DC Rainmaker Analyzer.
Both were beeping for lap splits pretty close to the mile markers on the course, but the Garmin ended up reading very slightly short of the marathon distance, while the Apple Watch Ultra 3 was long.
In general, you run longer than the official race route with most events because you don’t take the tightest possible line around corners, and I’d say even though the Fenix 8 Pro was closer to the actual marathon distance, the Apple Watch Ultra 3 might be closer to how far I actually ran.
Looking at the GPS tracks there are a few spots where the Fenix 8 Pro seemed to smooth out bends in the road that might have shaved some distance, but this is all very marginal and I’d say both were excellent for GPS accuracy overall.
The same is true for the heart rate readings on the watches. I didn’t wear a chest strap to compare them, but I have run 16 marathons now and have worn a strap in the past, and know what to expect with regards to my heart rate.
Both watches showed a steady rise overall, peaking at the end as I hit my max effort and heart rate. In the first half of the race there were some sharp hills and my heart rate jumped around a bit as a result. In that section, I think the Fenix 8 Pro was a little smoother and more accurate than some of the jumps on the Ultra 3, but overall both were largely aligned throughout the run, both with each other and my expectations of where my heart rate would be.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: Connectivity
Both watches offer LTE and satellite connectivity which require a subscription — with Garmin this is done through the brand itself, whereas with the Apple Watch Ultra 3 you get it through a separate provider.
One important difference is that Apple allows you to send SOS messages for free (for two years), whereas with Garmin you need to have an active subscription to send them.
Another difference is in the location sharing you do on the watches without your phone nearby. You can share your location with FindMy on the Apple Watch, but Garmin’s LiveTrack feature is a bit more developed and a great way for people to track you during outdoor activities.
I had LiveTrack enabled for the marathon, having left my phone in my bag, and when I started the race it automatically contacted my wife to let her know my LiveTrack was running. Then she could see my location along with info like my pace, distance and heart rate during the marathon.
It’s primarily a useful feature for safety reasons, but also makes tracking someone during an event like this easier, though it does hit battery life hard. Speaking of which…
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: Battery life
The Apple Watch Ultra is listed as lasting 42 hours, but I actually found it lasted me the whole three days of my trip for the marathon, only running out of battery as I was traveling back from the airport near my house.
I had the screen always-on throughout this time, and tracked the marathon in the normal GPS mode. On race day morning I had 51% battery left, which dropped to 27% after the race.
It’s impressive for a true smartwatch like this, though still short of the battery life offered by the Fenix 8 Pro, which I also charged on the Friday before the trip and still had 33% left when I got home on Monday.
During the race the Fenix 8 Pro burned through 22% of its battery life. I was using the most power-intensive GPS mode and had the LiveTrack running and the screen always-on, which means I’d get 10-11 of tracking in total.
That’s impressive given I did have the location sharing on, and you can easily extend the GPS battery life on the Fenix 8 Pro to over 20 hours with different settings, or over 30 hours if you turn the always-on display off.
The Apple Watch Ultra 3 can track for up to 35 hours in its low-power mode where it takes fewer GPS and heart rate readings, which can be useful for long hikes in particular.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: Smart features
One thing that did come across during the marathon weekend is that the Apple Watch Ultra 3 is a smarter and more useful watch to have, especially when traveling. It showed my boarding passes for the flights I took, and Apple Pay is easier to set up and use than Garmin Pay.
The Garmin has a lot of useful smarts including music storage and its native navigation features are better than the Apple Watch Ultra’s, but it doesn’t have much of an app store and things like messaging or checking emails are easier on the Apple Watch.
Apple Watch Ultra 3 vs. Garmin Fenix 8 Pro: Verdict
While the gap between the different strengths of the Garmin Fenix and Apple Watch Ultra grows smaller with each generation, there is still a gap. The Apple Watch Ultra 3 has more smart features and slightly more comfortable and elegant design, but lacks the battery life on the Fenix 8 Pro along with its more advanced training analysis features.
Both performed well for accuracy during the marathon, and you could definitely rely on either to be your running watch. You get more depth of analysis with the Garmin though, while the Ultra 3 will be more handy to you when you’re not working out.
A major plus to the Apple Watch Ultra 3 is that its price has stayed the same as past models, whereas the Garmin Fenix has gotten more and more expensive. The two watches used to be quite similar in price, but now the Ultra 3 is $400 cheaper than the most affordable Fenix 8 Pro, and that could well be the deciding factor in which you opt for.
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