The GPS-overlays are sweet. I have a GPS one and a non-GPS one. Completely different form factor, works well for handholding and streamlined (less turbulence) when mounted into the wind.

From what I've heard, both are good, Garmin won't give you 4k (After playing with 1080p for months, I've gone to 720p anyways for economys sake (both in hard drive space and processing/editing time), but Garmin does give you the GPS overlays.

There are a few other brands of action cams out there, but when I did my research it was between the Garmin and the GoPro, with GoPro being the most popular, just lacked some features (and form factor) that I wanted.