Kinda depends on what you’re after really. The GoPro has a lot more options when it comes to places to mount it whilst riding (helmet, chest, frame etc.), but the contour is certainly less obtrusive and (i think) you can use a smartphone to wirelessly check the set-up angle etc.
When I was buying a year ago, I went for the GoPro – from the comparison videos I found, it had much better colour contrast and general quality, plus it does other things like taking photos/time lapse photos etc. The new Hero2 looks even better – more options in terms of quality (720/960/1080), frame rates and recording angles (from three ranging from 90 to 170, i think). Don’t know how much the contour has improved in that time, but I’d happily buy another GoPro.