IMHO the decision to buy should be made based on what games you want to play, not what the hardware can do. Sure, the PS3 can throw around more polygons per second than X360, or can do more picoflops of computation, but so what? People place far too much emphasis on looks ("Is it HD? What kind? 480? 780i? 1080p" or "wow - is it using hardware accelerated High Dynamic Range lighting model" or "is that real time ragdoll physics") rather than gameplay.
This is part of the reason why Nintendo doesn't enter the hardware arms race (the Wii technology isn't a huge leap forward in technological power as its predecessor the GameCube) - they realised long ago that the only thing that matters is gameplay.
I'll be buying a Wii for sure. I have an X360 already. I will probably get a PS3 in a couple of years when the price has fallen and the software base is mature. Having said that, I understand that not everyone can afford to own all the consoles and needs to make a choice, but choose wisely - look at the PSP; even though it is technologically superior to the Nintendo DS - it's a dead duck in comparison (DS outsells PSP by a factor of 5 to 1 worldwide) because the games (i.e. the fun that you buy - the whole reason to own a gaming device) just isn't there.
Currently playing Gears Of War on X360.
