I switched from the Garmin 610 (paid for it, somewhat of a discount from working in Run Specialty) to the Nike GPS. I got the Nike Sportswatch for free from my rep and gave it a shot not expecting to switch. I had worn the 610 for right around 1000 miles. Accuracy was the same for both, worn at the same time and clicked at the same time and they clicked miles within 5 feet of each other. The Nike just felt and looked sleeker in comparison. I know the 10 is smaller than the 610, so size/shape may be less of a factor.
They gave me all the same features, since I didn't need the extra display or the heart rate function that the Garmin gave me. I use a regular non-gps watch for my track work anyway.
Anyway, I like the Nike watch more than the Garmin, but I have seen more returns for Nike, despite having never had an issue with mine. I wouldn't make the statement that the Nike isn't for serious athletes, though.
Either one would be great, but might as well try something new this time!