They are both good in their own way, Wii is far more fun to play, if graphics and stuff consoles can do are more your thing then PS3 is better for that.
I have both and I play my Wii far more because the PS3 just doesn't have a good library of games yet, I get bored quick with the current games.
The PS3 isn't really overpriced like everyone thinks, just for a games console then it is but it is also a bluray player, an actual bluray player costs around Ãƒâ€šÃ‚Â£700+ in UK and a PS3 is only Ãƒâ€šÃ‚Â£400 so if you were to go out and buy a bluray player then PS3 is the best option as you get a bluray player and a console in one for almost half the cost of an actual bluray.
For people who have no games console yet and wish to go buy a console I would say either Wii or 360, Wii because of the fun and the games library is picking up pretty well and I say 360 because the games library is just huge right now for the moment.
If you were planning on a PS3 then personally I would wait a year or so until more games are out, if I didn't get mine cheap I prob wouldn't of had a PS3 yet.