I ran a half marathon with the Apple Watch Ultra 4 and Samsung Galaxy Watch Ultra 2 — here's the one that came out on top

(Image credit: Future) If you’re looking for a smartwatch that’ll double up as a sports watch for your next race, you’re probably choosing between the Apple Watch Ultra 4 and the Samsung Galaxy Watch Ultra 2. We’ve reviewed both on Tom’s Guide, but to find out more, I strapped both to my wrist and ran a half marathon — read on to see which came out on top. The Apple Watch Ultra 4 is Apple's latest rugged adventure watch, with a new heart rate sensor and a daily Readiness score. Samsung Galaxy Watch Ultra 2 The Samsung Galaxy Watch Ultra 2 is Android's toughest smartwatch and a big improvement on the original Ultra. When deciding between the two, note that the Apple Watch Ultra 4 requires an iPhone, while the Galaxy Watch Ultra 2 works only with Android or Galaxy.Both have a large case — 49mm for the Apple Watch Ultra 4 and 47mm for the Samsung Galaxy Watch Ultra 2. Both have built-in GPS and track your sleep, stress, workouts, recovery, and more. The Apple Watch Ultra 4 costs $799, whereas the Samsung Galaxy Watch Ultra 2 is $699. But which is most accurate? Let’s find out.I ran a half marathon with the Apple Watch Ultra 4 and Samsung Galaxy Watch Ultra 2: Here’s which came out on top GPSLet’s start with the basics — if you’re wearing a watch to track a race, you want it to track your GPS pretty perfectly. When putting both devices side by side, the GPS is pretty much spot on for both, and this shows when comparing the recordings to the actual map of the course.With both watches, I had auto-lap set up, and both were pretty much hitting the distance markers at the right point. Of course, both watches recorded a slightly longer distance than the actual race itself, but this accounts for weaving runners and not ever really being able to stick to the race line. The Apple Watch Ultra 4 recorded the run as 13.23 miles; the Samsung Galaxy Watch 2 recorded it as 13.21 miles. (Image credit: Dan Bracaglia/Tom's Guide)Heart rate I didn’t wear a chest strap with the two watches, so I’ll use my Oura Ring 5 as my baseline. According to my Oura Ring 5, my average heart rate was 163 beats per minute, with most of my time spent in zones 4 and 5, showing I was pushing myself throughout the run.The heart rate graphs on the Apple Watch Ultra 4 and Samsung Galaxy Watch Ultra 2 also look pretty similar, with my average heart rate on my Apple Watch recorded as 159 beats per minute and my Galaxy Watch recorded as 160 beats per minute.Get instant access to breaking news, the hottest reviews, great deals and helpful tips.Again, this one is pretty much too close to call. (Image credit: Future)ElevationOne thing that my colleague, Dan Bracaglia, found when testing the Samsung Galaxy Watch Ultra 2 was that the elevation gain seemed inaccurate during his runs and rides. I didn’t find the same — the official course route has a total elevation gain of 311 feet, and my watch recorded the run as 342 feet. Similar to GPS, a small difference is often down to altimeter sensitivity, GPS drift, or weaving through runners on the course.Comfort and usabilityI’m a pretty petite runner, and both watches felt pretty chunky on the wrist. Design-wise, the Samsung Galaxy Watch Ultra 2 felt a little wider, but it doesn’t have much in it.Both have those all-important physical buttons that make using the watch with sweaty fingers a little bit easier, and both have bright, beautiful screens that were easy to see, even in direct sunlight. You do see slightly more on the screen of the Apple Watch Ultra 4, which is bigger, but again, there’s not a lot in it. (Image credit: Future)Which should you buy? The answer really depends on whether you’re team iOS or Android. If you have an iPhone, don’t buy the Galaxy Watch Ultra 2, as it won’t work with your phone. Both are like having an extension of your phone on your wrist, with tonnes of apps at your fingertips.Both did a stellar job of recording my half marathon, and both are probably the top contenders if you want a smartwatch with the capabilities (but sadly not the battery life) of a sports watch.Follow Tom's Guide fitness on Instagram for more workouts, routines, tips, and tricks. Follow Tom's Guide on Google News and add us as a preferred source to get our up-to-date news, analysis, and reviews in your feeds. More from Tom's GuideI trekked the Cascade Mountains with the Apple Watch Ultra 3 vs Garmin Instinct 3 vs Samsung Galaxy Watch Ultra 2 — this is the one I'd take on my next hikeGarmin Cirqa vs Fitbit Air vs Whoop vs Oura Ring: Our fitness experts are helping you pick the perfect fitness trackerI walked 4,000 steps with the Apple Watch Ultra 3 vs Samsung Galaxy Watch Ultra 2 — and the winning margin was razor-thin Jane McGuire is Tom's Guide's Fitness Managing Editor, which means she looks after everything fitness-related - from running gear to yoga mats. An avid runner, Jane has tested and reviewed fitness products for the past ten years, so knows what to look for when finding a good running watch or a pair of shorts with pockets big enough for your smartphone.