I ran my sixth marathon last weekend — the 2026 London Marathon, and, ever the tech tester, I decided to strap two watches to my wrist for the experience. Sure, it raised some questions on the start line, but the London Marathon is a great test of how well watches really cope with crowds, skyscrapers, and 26.2 miles of recording data.
For the run, I wore the Apple Watch Ultra 3 and the Garmin Forerunner 570. Both watches have bright, beautiful displays and dual-band GPS, designed to boost tracking even in challenging environments.
There are some big differences, of course — the battery life on the Forerunner 570 is far superior to the 36-48 hours you get on the Ultra 3, and the Garmin watch is packed with advanced training features, suited to runners of all levels. It’s also cheaper at $549 versus the Apple Watch Ultra 3’s $799 price tag.
That said, the point of this test was to look at how well Apple versus Garmin performed over the run. The London Marathon is notorious for being a GPS dead spot, and is conveniently positioned between miles 19-21 of the London Marathon — a time where you really don’t need GPS mind games.
Below, I’ve crunched the data and compared the usability of the watches over my run. Read on to find out more.
Apple vs Garmin: GPS
Both watches recorded a total distance that was impressively close to the official marathon distance of 26.219 miles, but the Apple Watch Ultra 3 was a fraction closer, recording a run of 26.54 miles.
The Garmin Forerunner 570 clocked the marathon as 26.57 miles. Either way, this extra distance reflects the fact that, when running with 59,000 other people, it’s impossible to stick to the racing line, and you inevitably add extra distance weaving around runners.
Both watches were hitting mile splits quite close to the markers on the course at the beginning of the race; it didn’t take long for this to change. I was manually lapping my Garmin and found that by the final few miles of the race, my Apple Watch was reaching the mile marker about 0.25 miles ahead of me.
As mentioned above, the hardest part of the course for GPS accuracy is around Canary Wharf, where there are a lot of tall buildings that block satellite signals, and when going through the Blackfriars Underpass.
On both watches, my split pace went haywire around this area, both recording me running around an 8:40-minute/mile, not the 8:00-minute/mile pace I’d been hitting consistently throughout the race. This wasn’t as bad as I’ve known it to be in previous years, and both watches recorded my average pace throughout the marathon as 7:55 minutes/mile (Apple) and 7:54 minutes/mile (Garmin).
Apple vs Garmin: Heart rate
While I didn’t wear a heart rate monitor on race day, both watches recorded my heart rate as 185 beats per minute. Both recorded my max heart rate in the final few minutes of the race as I sprinted to get across the line in under 3 hours 30 minutes (I missed it by three seconds, but let’s not dwell on this), as 202 beats per minute.
Overall, these stats are in keeping with data I’ve seen during my training.
Apple vs Garmin: Usability
I’ve trained with both watches, so I was used to navigating around both on race day. When running a marathon, I always opt to manually lap my watch, as you end up running further than the distance itself. For this challenge, I let the Apple Watch run and just manually lapped the Garmin. You can set up the Action Button to mark segments on the Apple Watch Ultra 3.
Both watches were also easy to read, even in bright sunlight, as it was a warm and sunny day.
Apple vs Garmin: Verdict
Overall, both watches performed well on race day, and this one is almost too tough to call. I’d say the Garmin Forerunner 570 was ever so slightly more accurate in terms of hitting the mile markers, but there’s not an awful lot in it, and both of these watches were great on race day.
Of course, the Garmin offers a little more in terms of training features and battery life, and is considerably cheaper than the Apple Watch Ultra 3. The Apple Watch Ultra 3, on the other hand, is an excellent smartwatch — it’s like having an extension of your iPhone on your wrist, with all the apps you could ever need. I loved getting messages of support pop up on my Apple Watch throughout the race, and if I really wanted to, I could have replied to them on the move.
Either way, whether you’re an Apple Watch Ultra fan or you’re sticking with Garmin, either will do a great job on race day.
