Vista is resource hungry but handles the memory better. having said that i'm sticking with XP on the PC because I simply don't like vista. It reminds me of windows ME compared to '98

I have used Macs for years and if you can afford it i would say go for a mac. The only reason I went for an upgraded PC was because I have so much PC software. When this baby dies I will be going back to a mac. Speed is really not much of an issue with PC's these days. But there is something solid and reliable about a mac. Yes they can freeze and yes there are a handful of viruses but compared to the PC the mac sings a better tune.
I'm running quad core processors and 4 gig of RAM. My mates Mac still runs smoother, not faster but smoother. No hang ups and the machines are pure eye candy !! yum yum.