I think the best advice i could give would be to do a lot of research on this yourself before deciding on what to go with. I could point you to different reviews and such but i think it's more important for you to go through and really search for yourself. If you really want/need some help finding some information i can point you in the direction of some reviews and such but as i said before i wouldn't recommend that.
As far as my personal preference.....either one really. They both are great cards and each have their strengths and weaknesses. If you go with ATI then i'll just say that some people have still having some driver issues with them but their releasing new and better drivers all the time but for now you might have to put up with some annoyances that come with the card but then again you might not. The original GF3 doesn't really have quite the power the 8500 does but it's not far off and it has good driver support for it. (Just 2 of the bigger differences between the 2). However, whether you go with one or the other, i would wait. With the new generation of cards coming out from both companies i would wait until the prices come down to get a cheaper buy.
One last word of advice. Don't go on 3dmark scores alone. There are many other things to take into consideration than 3dmark and many other benchmarks too.