In Nick Harris-Fry’s Frankfurt Marathon run, the COROS PACE 4 Pro recorded 42.52 km against the course’s stated 42.19 km, while the Apple Watch Ultra 4 recorded 43.07 km. COROS came closer in this one-race comparison, according to Harris-Fry’s report for Tom’s Guide, published November 5, 2026.
COROS recorded closer to the stated course distance
| Reported measure | Apple Watch Ultra 4 | COROS PACE 4 Pro | Conditions |
| Recorded distance | 43.07 km | 42.52 km | The stated course distance was 42.19 km. |
| Distance above the stated course figure | 0.88 km | 0.33 km | Calculated from the reported totals. |
| Battery used during the race | 16% | 10% | Apple started at 75% after a charge from 41% and played music for about an hour. COROS started at 75%. |
The distance totals favor COROS for this race, not as a universal GPS ranking. Harris-Fry says both tracks went astray among tall buildings during the first and final 5 km through Frankfurt’s city center. The Apple track cut corners and strayed from the road more often.
A closer course total is useful for this race; it is not a universal GPS verdict.
Battery use during the race
The reported drain was 10% for COROS and 16% for Apple, a six-percentage-point difference. Apple began at 75% after being charged from 41% and played music for about an hour; COROS also started at 75%. That makes the figures a record of this particular race and use, rather than a general battery-life estimate.
Heart-rate readings were not checked against a chest strap
The race comparison does not settle which watch measured heart rate more accurately. Harris-Fry wore arm sleeves and did not use a chest-strap reference. He thought Apple’s heart-rate trace looked more plausible overall, except for a long gap between the one- and two-hour marks. He judged the COROS trace too high and too flat. Those were his impressions of the traces, not a reference-based accuracy measurement.
Running priorities versus smartwatch features
The reported specifications favor COROS for weight and multi-band GPS battery estimates. Tom’s Guide lists the Apple Watch Ultra 4 at 63 g and 49 mm, and the COROS PACE 4 Pro at 51 g and 47 mm. Both watches have three buttons, including a dial.
| Dimension or battery mode | Apple Watch Ultra 4 | COROS PACE 4 Pro |
| Case size | 49 mm | 47 mm |
| Case thickness | 12 mm | 11.8 mm |
| Case weight | 63 g | 51 g |
| Multi-band GPS battery estimate | 18 hours | 30 hours |
| Smartwatch-use battery estimate | 50 hours | 21 days |
COROS’s smartwatch-use estimate falls to seven days with the always-on display. These are reported estimates for different operating modes, separate from the race drain above.
For everyday smartwatch functions, Harris-Fry describes Apple as offering App Store access, streaming music, NFC payments, boarding passes and more watch-face customization. COROS can store MP3 files for Bluetooth playback. In rain, he found Apple’s touchscreen less convenient for menus. Its buttons handle pause and lap, but ending a run requires the touchscreen.
Base PACE 4 owners describe separate experiences
Individual owners of the base COROS PACE 4 have described doubts about wrist-based heart-rate readings and delays in pace updates. One owner said interval workouts were straightforward to enter before a track session and review by lap afterward; another preferred a nylon band because it felt lighter and dried faster. These are personal accounts about the base PACE 4, distinct from the PACE 4 Pro used in the marathon comparison (owner discussion and track-workout and band discussion).
