Four GPS Watches Put to the Marathon Test: Garmin Fenix 7X, Apple Watch Ultra, Enduro 2 and Suunto 9 Peak Pro

Introduction

Marathon day is one of the harshest tests you can give a GPS sports watch: hours of continuous tracking, questionable weather, and a marked course you can measure the results against. That is exactly what four flagship watches faced in this comparison: the Garmin Fenix 7X, the Apple Watch Ultra, the Garmin Enduro 2 and the Suunto 9 Peak Pro. The result was a steady 3:01 run through genuinely wet conditions, giving a real-world read on screens, controls, GPS accuracy, heart rate and battery drain.

How We Tested

The plan was simple: wear all four watches through a full marathon, run entirely on feel rather than following the watches, and compare the data afterwards against the official course distance. Testing covered screen legibility in heavy rain, control usability with soaking wet hands, GPS distance against a certified course, heart rate consistency, and total battery drain from leaving the charger to crossing the finish line.

The weather turned out to be an accidental bonus. Persistent rain exposed real differences in how each watch’s screen and touch controls hold up when everything is soaked, which is something dry benchmark tests rarely capture.

Screen and Display Quality

The ranking here was clear. The Apple Watch Ultra has the best screen of the group: vivid, punchy and easily the most legible, especially in gloomy conditions. The two Garmin watches come second, and it is a genuinely strong second. Both the Fenix 7X and Enduro 2 offer lots of screen real estate, much improved brightness and good colour, and there is very little to choose between them.

The Suunto 9 Peak Pro trails the field. The display feels dated, it is not as bright or as easy to read, and the large bezel eats into the usable screen area. On a dark, wet morning it was the hardest watch of the four to glance at mid-run.

Controls in Wet Conditions

Rain made this category matter more than usual. The Garmin approach of combining a touchscreen with physical buttons won out: when the screen became unreliable, the button zone made it easy to control everything without fuss.

The Apple Watch Ultra sidesteps part of the problem with its dedicated action button, which can be set to launch a workout directly. One press plus one tap and the run was recording, which was genuinely useful in the chaos of a race start.

The Suunto 9 Peak Pro relies partly on its touchscreen for controls, and that became a real problem when soaked. Combined with the button setup, the interface never felt fully resolved in bad weather.

GPS Accuracy on a Marked Course

This was the most reassuring result of the test. All four watches recorded a distance very close to the official marathon measurement, well within the normal margin of error for consumer GPS. The Apple Watch Ultra came closest at 26.26 miles, with the Enduro 2 and Fenix 7X at 26.34, and the Suunto 9 Peak Pro landing at 42.38 kilometres. All four sat comfortably within range of the certified distance.

A check of the route maps for anomalies, like drifting through buildings or into rivers, turned up nothing on any of the four watches. On GPS alone, there is essentially nothing to separate them.

Heart Rate Performance

The Fenix 7X was paired with a chest strap for this run, leaving the Enduro 2 and Apple Watch Ultra’s optical sensors to be compared directly against it. Both performed remarkably well. The Enduro 2 matched the strap identically on both average and maximum heart rate, while the Apple Watch Ultra matched the average and missed the peak by only a couple of beats.

Mile-split averages also tracked closely across the whole race, with no dropouts or erratic spikes on any of the three logging heart rate. One caveat: the Suunto 9 Peak Pro produced no heart rate data for this run because the optical sensor had been switched off for a separate battery test and was not re-enabled before the start, so it cannot be judged on this category here.

Battery Drain Over Race Distance

Over roughly three hours of running, the Garmin Enduro 2 and Fenix 7X were the clear winners, each using just six percent of battery. The Suunto 9 Peak Pro used eight percent, but that was with the optical heart rate sensor, backlight, notifications and several performance settings switched off to stretch endurance, so the real-world figure with everything active would be higher.

The Apple Watch Ultra consumed 27 percent during the run itself, plus another five percent getting to the start. Notably, that total is still an improvement over previous Apple Watches, and it means the battery now comfortably survives a full marathon with smartwatch features still available afterwards.

Which Watch Should You Pick for Marathons?

The Fenix 7X and Enduro 2 are almost interchangeable for marathon purposes: similar battery life, similar hardware, similar GPS performance. If you do not need smartwatch extras and are choosing between the two, the Fenix 7X typically comes in at a lower price, which makes it the logical pick of the pair.

The Apple Watch Ultra is now a genuinely credible marathon watch, mainly thanks to its improved battery. You can run the full distance and still have phone, music, payments and all the other smartwatch features available at the finish, even if you leave your phone at home.

The Suunto 9 Peak Pro is the budget option of the group at around £459, roughly half the price of some watches here, and it will reliably track a marathon distance. But the dated screen, large bezel and awkward controls in poor weather hold it back, and it is hard to recommend over the others despite the price advantage.

Conclusion

All four watches measured the marathon distance accurately, so the differences come down to everything around the run. The Garmin Fenix 7X offers the best balance of battery, controls and price among the sports watches, the Enduro 2 matches it almost exactly, the Apple Watch Ultra wins on display and now lasts a full marathon, and the Suunto 9 Peak Pro remains the affordable fallback for runners who mainly need reliable distance tracking.