I own both the Contour and the GoPro Hero HD. I also am an authorized retailer for both brands.
I feel that they are obviously both great products. I think if you have to choose between the 2, it comes down to how you want to mount them. The contour is longer an skinnier, whereas the GoPro is short and stubby. Because the GoPro is short and stubby, it is able to be used with such mounts as the Chesty chest mount harness, wrist housing, head strap mount, helmet front mount, etc. These mounts would not work as well with the Contour because it is too long. However, the Contour excels when mounting to side or top of something like a helmet because it will stick out much less.
When it comes down to the actual footage of a GoPro vs ContourHD, I asked Norbi Vasko in another wakeworld post (He has made a ton of wake videos - Here is his Vimeo
I asked Norbi Do you prefer the GoPro HD Hero or the ConturHD and why. He stated,
"Contour HD all the way !
Lighter, way better mounts/adjustments, better light metering options, editing software works on mac/pc, better bit depth/resolution/sharpness settings, you can have 2 presets and with 1 button switch between the 2. the lens turn 145 deegress so you can fit the camera basically anywhere and get the sickest angles. it has laser pointers so u always know where ur shooting. better, smaller and lighter memory sticks. the actual shots are not distorted noob looking wide wide wide angles where you loose depth perception but instead a nice square ish frame with still a wide 135 degree angle point of view. I just love it and I could keep going all day but I gotta go export the latest video with more unseen contour footie. be on the look out. contour HDs gonna go great things. they already have the gps ones where you can exactly track youre route and more!
I also read a post from a mountain bike blog that Contour is working on a new Countour GPS. The article and pics are here
Bottom line, both brands are awesome. I really think it comes down to how you are going to mount it.
Please note - the Contour GPS does not have a waterproof housing available currently. They are working on it and it should be done soon.