If you want to have a remote, firewire support, and plan on playing games (and feel the need for speed) get the AIW 8500. If you just want to capture video, want a decent video card, and lots of features, get the AIW Radeon. Both are very much the same in video preformance, the 8500 just adds features such as the remote, firewire, the ablility to have your TV out and Monitor out at different resultuions, and a faster GPU. The ATI site, by the way, states that the AIW Radeon does not support HD TV Output, but if you look at the original specs, all you need is the DVI to Component Convert (which they Plan on selling) and you should be able to have the same output as the more expensive 8500 modle.
If it works for you then don't fix it.