I wore 4 top smartwatches through a Spartan race, 12 miles of running, and sleep tracking to find the ultimate fitness companion

"Hold on, hold on. What's going on here?" my coach asked as he noticed me wearing four watches before I went out running. I often wear two watches to the gym because I'm constantly comparing them, but I've never worn four before, and that was clearly enough to raise eyebrows.

After explaining the article you're currently reading, in which I wear four smartwatches through a series of tests, he laughed and told me I must have a fun job. Indeed, I do! But the results of the test should be a real help to anyone looking to buy a smartwatch this year (and help save some money in the process).

So stick with me as I run through my past week, in which I wore four smartwatches to sleep, every time I ran during my half-marathon Spartan training, and during a full 5K Spartan race over the weekend.

Starting off with a good night's sleep

I would never recommend sleeping with four smartwatches on, but I will say that it wasn't nearly as uncomfortable as I had been dreading. Most smartwatches collect the same sleep data, but every so often you'll find a watch that does something different. The Galaxy Watch Ultra 2, for example, included a skin temperature measurement, measured against a baseline it had determined in the past 2 weeks since I started wearing it.

Of all the watches I wore, the Honor Watch 6 showed the least data. Most of it is holed up in a sleep analysis section that gives you percentages and glanceable "normal," "high," and "low" ranges so you don't have to dive deep. That's good because I couldn't figure out how to dive deep into this data.

The OnePlus Watch 3 43mm offered a better look at the data, but it didn't include as many data points (like SpO2 or breathing quality). The Galaxy Watch Ultra 2 did a great overall job, but it seems like it's a bit more sensitive to my restless sleep than the other watches.

Overall, I felt like the Amazfit T-Rex 3 Pro's data was the most accurate. I know I woke up more than 2 times (which the Honor and OnePlus watches say), but there's no chance I was up 18 times as Samsung suggests. The T-Rex 3 Pro has a temperature sensor onboard, but apparently, it doesn't include this data for sleep. Weird choice, but that terrible 54 sleep score lines up with how I felt when I woke up, not the 72 Samsung gave me.

Time for a run (or four)

I began training for a Spartan Beast a few weeks ago using Amazfit's incredible running coach feature because I already felt confident in the watch's ability to accurately measure everything. Since I had already been comparing the Amazfit T-Rex 3 Pro to every other watch I've worn over the past few years, it made sense to keep it on for this comparison.

My intuition wasn't wrong. Looking at the map data above, where I ran 2.5 miles over two loops around this Walmart and the surrounding business park, things look pretty even until you zoom in. I broke off sections of the track so you can see the GPS tracking discrepancies between the watches.

Overall, the OnePlus Watch 3 43mm was the least accurate (genuinely a surprise to me), while the Galaxy Watch Ultra 2 and Amazfit T-Rex 3 Pro tied for first. The Honor Watch 6 also did an excellent job, but there were two points on the map with notable tree cover that showed me running in the road instead of on the sidewalk, while the other two kept me on the side of the road.

As I dove deeper into the rest of the data, I found a consistent pattern among all four watches. In each data point, there was a clear outlier. The Honor Watch 6, for example, got the altitude all wrong, while the Galaxy Watch Ultra 2 completely fumbled the cadence measurement.

The OnePlus Watch 3 43mm had some very strange spikes and dips in speed, almost assuredly owing to the GPS tracking issues I mentioned earlier, while all four watches tied for heart rate accuracy. Notably, the Amazfit T-Rex 3 Pro didn't show up as an outlier on any of the data points, owing to its excellent overall accuracy.

One Spartan Race to finish it off

As I approached the Spartan Race, it was clear that Amazfit and Samsung were leading the pack here. Since I had to wear an RFID bracelet and a separate time bracelet for the race, I only had room for two smartwatches, so this was going to be between the winners.

I don't see any obvious discrepancies in the GPS data between the two watches. Clearly, each is slightly different from the other, but it's impossible to tell which one is right since this is a trail course. I'll give this section a tie.

You'll need to click the expand button on the image above and zoom in to see all the details, but once you do, you'll understand why Amazfit did a better job of tracking this race. In the heart rate data, you'll see three points where the Galaxy Watch Ultra 2 did something weird. Just after 9:20 and around 10:05, it registered a far lower heart rate than I actually had.

Then, around 10:46-10:50, it seems to have failed to get a heart rate at all. Strangely enough, that same lapse in data also appears in the speed and cadence graphs. While both watches were dead-on with speed data and mostly similar with altitude, the Galaxy Watch Ultra 2 wildly messed up my running cadence, which happened during other runs I've gone on with this watch, too.

This particular Spartan Race was both very busy and extremely muddy, causing quite a bit of backup at each obstacle. On the cadence graph, you can see where the Amazefit T-Rex 3 Pro properly measured me not moving while waiting in line, yet the Galaxy Watch Ultra 2 seems to think these moments didn't happen. Trust me, I was frustrated enough to remember them, and that's enough to give the T-Rex 3 Pro the win.

Truly amaze

The Amazefit T-Rex 3 Pro has been my go-to smartwatch for the past two years, and it's no wonder, with the results I've seen over the past week. While several watches have caught my attention since then, this one is consistently the most reliable and one of the most feature-rich.

Aside from being a great watch, the Zepp app that powers the experience is second to none. The UI is excellent; it's got a ton of amazing features (like this AI-powered food logging feature), and the subscription is only necessary if you want additional AI-powered insights, which I haven't typically used in the past. All in all, it's easily my favorite workout companion and an experience I think fitness fans will love.