ATi's drivers are far more superior than nVidias. The only time i've heard that nVidia's drivers are..... "somewhat ok" are when using an 8 series card.
I haven't tried their drivers in awile as i'm using ATi now, but a friend of mine described every single bug with the nVidia display drivers that I had 5 months ago..... :X
But yeah, a videocard that doesn't steal from system ram should be mandatory.