My major moves are long day hikes in the Sierra Nevada. Having done a few with the Ambit2 and Suunto Trackpod, here are the accuracy results.
Hike 1--Granite Lip: 16 miles RT, 5300 ft. net elevation gain
Ambit2: Worn on right wrist
Average EHPE: 9.00 meters
Warmup time: significant (basically the whole 5 hour trip to the park)
Trackpod: Mounted on top of stick on my pack, about head height and about 6 inches from my left ear.
Average EHPE: 4.47 meters
Warmup time: about 30 minutes an hour before getting to the park, and then only 5 minutes before starting
So you can see that the Trackpod accuracy was about double that of the Ambit2, even though it had less warmup time. Obviously the favorable mounting position was the reason.
Hike 2--Kennedy Pass: 24 miles RT, 6400 net elevation gain (trailhead is only about 13 miles from the other one)
Ambit2: worn on chest strap, about 3 inches to the right of the Motorola Ant+ HR belt coupler
EHPE: 4.99 meters
Warmup: An hour or so
Trackpod: Same mounting position
EHPE: 3.87 meters
Warmup: an hour
Garmin 62sc: worn in pouch on upper left chest
EHPE: unknown, but prevailing accuracy was 8-10 feet, with as low as 24 feet under heavy tree cover. I would guess average EHPE around 10 feet or so.
Warmup: 5 hours
So the Garmin and Trackpod performed with about equal accuracy, even though the Trackpod was in a slightly better position for sat reception. Likely the Garmin has a superior antenna and would perform better under the same mounting positions.
Even though the Ambit2 accuracy was not as good, it was much improved over wearing it on my wrist.
HR dropouts on Ambit2:
Worn on wrist on Granite Hike: zero HR readings turned up in 2.6% of the xlss log
Worn on chest strap near the HR monitor: When the pack was being worn, only 0.7% dropouts occurred. However during breaks, the watch was left on the pack so I got a lot of zero readings during that time. Not sure if it's worth it to keeping moving the Ambit2 to my wrist during breaks and then putting it on my chest strap, in order to get better data, but considering I'm also getting better GPS accuracy, it's going to stay on the chest strap while moving.
Better HR monitor syncing is the reason I wore the T6 this way as well, but the problem is worse with the Ambit. Unfortunately, I couldn't use the trusty T6 to measure HR because I wanted to use the Garmin for that, as it will record track/HR/Temp every second. I'm hoping that Suunto will release an Ant+ HR belt in time for next year's hiking season. In the meantime, I'll use the Garmin + Ambit2 for HR on hikes, and the T6 + Ambit2 for runs.
Anyway, those are the results of my comparisons, FWIW. :)