Clicking the links would show that Xfire is free and fraps has both a free and paid version.
The free version of fraps is limited to 30 second video clips (I wonder when he added that, as I hadn't noticed it before...) and has a watermark along the top.
Xfire has no drawbacks (time limit, watermark, etc) that I know of. I'm not certain that it writes data in raw AVI format though. It also has the option for live streaming.
[edit: Xfire appears to capture the video in raw AVI format. They then offer a compressor that will encode the video down to smaller file size using their own "xfcodec" codec. That seems to be similar to XviD or DivX quality.]
[edit 2: Corrected the information from the first edit. Xfire does capture raw AVI. You can then either use it to directly compress the video or compress the video using another program, such as VirtualDub. Guess I'll try some Xfire capture tonight so I can actually be a bit more knowledgeable next time.]