well my hubby does computer repairs ect on the side and according to him the Wii Doesn't break as opposed to the xbox 360 which ended up with the red ring of death as they call it lol, though he knows how to fix the xbox but apparently the Wii doesn't break, so I'd say you're probably better off with that, though there are more games for and all have better graphics on the 360, so I suppose it really comes down to personal choice on a lot of factors..
Xbox360 - better graphics and more games
Wii - Doesn't break, more physically interactive
IMO a 360 would hold anyone's attention longer than a Wii, but I hear and see from close friends that it's also fun
so again...
Personal Choice..
If you get a 360 and it gives you the ring of death, let me know and hubby and I can walk you through the fixing (properly, not the youtube crap that's posted that we end up having to fix on top of the original problem lol) mostly it's been fixed though in the newer models... Just make sure to keep it from over heating and you'll be fine...
Which reminds me of a joke my grandfather told me once...
Microsoft Works LoL
Basically the 360 is a computer with controllers that graphically focused... I guess that's the best way to put it anyway
eta: ps3 is good for guitar hero, but in my opinion as an actual guitar player, it's for idiots.. I'd personally give any kid I will ever have something that will make them think and if they want to play an instrument, then I'd get them playing that instrument, not some controller that LOOKS like one but has 4 buttons.... A reg. guitar acoustic or electric has 6 strings( and yes I know there are variations, I used to have a 12 string), which is more than 4 buttons and WAY more combinations with the 23 frets on top of it instead of 4 buttons and MAYBE 10 frets and a button/lever that is supposed to simulate the strumming and plucking on a guitar AND the Whammy bar that SOME not ALL guitars have, and any with a whammy bar I guarantee will be electric or at the very least, a 'souped up' electric acoustic. Just my 2 cents... and yes I HATE GUITAR HERO AND THE EMO CRAP THAT IS BRAINWASHING TODAY'S YOUTH. This is just my opinion though lol