I ran an eight-week marathon block this winter and rotated three watches in real training, not demo mode. I wore each one for at least a full micro-cycle so I could see how it behaved on normal days, bad sleep days, and long-run days.
The three I used:
- Garmin Forerunner 965
- COROS Pace 3
- Apple Watch Ultra 2
My testing setup
I kept everything else constant:
- Same 10 km weekday route (city + bridge + tree cover)
- Same long-run route on weekends (18-30 km)
- Same chest strap for spot checks
That made comparison easier because pace drift and GPS noise were obvious when they happened.
What happened on long runs
Garmin was still the easiest for structured training days. Pace smoothing was stable and lap alerts were clean. COROS surprised me with battery confidence. I stopped checking battery before long runs, which sounds small but reduces stress. Apple Watch Ultra 2 felt smooth in everyday use, but during long runs with music + GPS, I had to think more about charge planning.
What happened on interval days
On track-like sessions, Garmin and COROS were both reliable enough for repeats. Apple was usable, but the way pace fluctuated in tighter turns made me glance at data too often. That broke focus for me.
Software and day-to-day friction
Garmin Connect gave me the most complete post-run review. COROS app felt faster and less noisy. Apple ecosystem integration was excellent for daily life, but my training workflow required more taps to see what I wanted.
Who each watch fits
- Garmin Forerunner 965: runners following structured plans and using pace zones seriously
- COROS Pace 3: runners who want high battery value and straightforward execution
- Apple Watch Ultra 2: iPhone users who value all-day smartwatch features as much as sport metrics
My final setup now
I keep Garmin as my primary training watch and Apple for non-running days. If I were buying only one today with budget in mind, I would choose COROS Pace 3 and never look back.
The biggest lesson from this test: consistency matters more than feature count. A watch that you trust every day beats a watch with ten extra metrics you never use.
Field notes from week 6 to week 8
- On a windy bridge route, Garmin and COROS stayed closer to perceived effort than Apple pace readout.
- For early-morning runs, screen readability mattered more than I expected, especially when my hands were cold.
- If I had to start over, I would disable non-essential notifications on all three watches from day one.
Most watch frustration was not hardware failure; it was poor setup discipline.