One thing in general I've noticed recently is Nvidia has been falling behind the ball on their old being known for reliability and making good products. ATI seems to be stepping up to the table recently and has made some great improvements in being compatible etc. I don't have lightwave so I can't check for you though specifically.
I used to dislike ATI's due to compatibility issues they had, but after getting my one 2000 something model a few years back, and now upgraded to my 5850 I have just been impressed by features, price, and stability. Especially since it took Nvidia over a year of delays to release fermi (directx 11 support), while ATI had their line out wayyy ahead and its drivers wern't the best to begin with, but they have definitely been stabilized. From what I know Nvidia's arn't quite as good yet since it just now released.
Definitely try a few google searches though when you pick out a few cards you like, and see how they perform with various programs you like benchmark wise.