i have a contour HD which i brought from ASGI, got it for a little under 200$ during the memorial day sell but with extra battery, and picatinny rail mount i payed 250$ that time. i've only touched a contour and gopro before so here is a comparison between them, of my opinion:
for the GoPro: the video has a slightly better quality than the contour, and of its mounting system; it is easier to come up with ways to adjust the angle of the camera to where you want. however since the shape of it is like a block it may seem awkward to mount it off center of the object you're mounting it on. for airsofting you would probably want to stick it onto a helmet that has NVG mount or a heavy weapon like a M240 or M134
as for the Contour: even though the video isn't as good as the gopro and aligning the camera is a bit tricky the audio recording is a lot better due to its multi-direction microphone thats built in it, the stream line of the body makes it perfect for mounting it on a gun or to the right side of your helmet/goggle (if you're right handed), also the recording button is less of a hassle than the gopro if you are using gloves
my airsofting videos are still being edited right now, all i have now is the video where my robotics club used it on a t-shirt launcher down below
http://contour.com/stories/t-luanch
although the contour is priced at 250$ if you're not in a rush to buy one. you could wait a while to see if you can get a better deal than what i payed for especially if you have time to wait for a Holiday.