The gowearfit has the sleep analysis, and I really loved that feature. It will show you how many times you wake throughout the night/for how long, lying down vs sleep, etc.
Since you are buying a device like this for data, I say the more data points the better. That's what ultimately swayed me towards the gwf.
Personally, I did end up returning mine. While the info was nice to know, the novelty of it wore off after a while and it was basically the same info everyday. Not something I could see wearing (and paying for) every day/month.