I dunno, I've had tons of problems with nvidia and Maya. Never used blender.
But not once have ATI failed me.
I'm currently running on an ATI1450 512mb.
(though I had to replace the fan because it sucked arse)
And it works perfectly with everything. Can even play new games on high settings. With my new cooler It's very overclockable. Running on as low as 40degrees celsius on full load, idle 20-30c.
With the standard fan it ran as high as 89 on idle and 110 during load. I thought it was gonna melt
Sorry, I lost track.
If you get nvidia don't get anything before geforce9800.
Get 64bit vista and 4gb ram for max potentiality :o
"Sadly, most artists prefer to give the elite their attention."