I would have voted, however, I'm leaning toward ATI right now because of their video processing technology. I just bought an ATI 3650 to replace a Nv7600 and the difference in video processing is phenomenal. There's not even a comparison between pictures. The 7600 was grainy and had a very hard time with black and contrast ratios. Any dark scene on any dvd was always pixellated and splotchy. The ATI card is as clean as can be.
T
Edit:
Sorry about the double post. I should also add this is my first ATI card I have ever owned. I've owned several motherboards, my first was a viakt133a, my second was an nforce, nforce2, and i now have 3 nforce 4 boards running. I've had a Geforce (the original), a 6600gt, 7600gs, and now this ATI card. It's great for htpc, it's and upgrade to the 7600gs it replaced, it's silent, it's cool running, and as I said, it whoops on nvidia' pure video in terms of video decoding and output.