Well, Wii has an extra mode or two, but 360 has presumably better online. If you don't care about graphics in a game like Guitar Hero, I'd suggest the Wii version but you certainly can't go wrong with the 360/PS3.

 PSN cards are available

^^This.

The games are going to be very similar.  I'm sure the 360 will have the most streamlined online but its not going to be a major advantage unless the PS3 or Wii online just stinks up the place. 

The only major difference is going to be that the Wii has the Mii Freestyle mode which I would have said 2 weeks ago was not worth mentioning but apparently I would have been wrong two weeks ago.  Here is an excerpt from the IGN hands-on:

...

It's a strange concept to describe on paper, but it really does work quite well. In fact, outside of the general "play as you go" notes and modes, you can also morph the experience as you jam, keeping specific riffs or tones you've hit in a constant repeat. Want to lay down a simple hold note progression in the background? Lay it down, and then hit the repeat trigger to keep it looping. Want to build on top of that backbeat? Just riff over it, and then cancel the beat whenever you want to move into a new phrase of music.

...

And if Freestyle didn't sound big enough, Vicarious decided to build on the mode once again by adding the drum kit into the mix. By either hooking up your full drum kit or using a variant on the Wii Music drum design (Wii-mote and nunchuk, with different buttons making different sounds when you motion; not our preferred way of playing, to be honest) you can freestyle with any backbeat, or accompany a friend on drums while he riffs on guitar. This opens up the drums in Guitar Hero to take the same form as Rock Band's "virtual drum kit" add-ons, letting you just sit down with your set, crank out your own beats or solos, and use the kit as a real electronic drum set. And yeah, just like the rest of the package, this added option also kicks a whole lot of ass.

With that pointed out I don't think the freestyle mode is a make or break type of deal.  In the end all 3 of the current generation consoles are going to provide a great experience and its going to come out about the same overall.  It all boils down to how you want to play the game, which consoles you own, and who you anticipate will be playing with you. 

If you have a more casual gamer who will want to play but might be intimidated by the main game or if you just want a more freeflowing jam mode the freestyle mode offers additional options for both.  You can turn your casual friend into a potential band mate or just jam out while you're drunk without having too work to hard to make it sound good.

But if you just want to jam with your buddies online then whatever system they're getting it on becomes the obvious choice.

In short, there is no best version based on the info we have right now, there are only better fits for specific individuals.

ps360

especially if you DON'T own a arcade.

since you won't have to buy a expensive harddrive or SD Card.

Uhm, $7 including shipping (90% 5/5 rating from over 230 customers) for a 2GB Kingston SD card is not really a big deal.  Not to mention the folks who need one will likely already have one.

2gb VS 20gb--->160gb.

2gb is not enough for games that + songs and packs it doesn't fit you will have to buy a few of them and  exchanging its annoying.

lets not forget the 16gb sd chip lets not forget the ps2 which people buy guitar hero for the most

Continue reading my post dude.................

So you went from saying that it is expensive to saying that it would be a hassle?  That seems an awful lot like a moving goal line =P

Considering that RB songs were 20-30MB and they have said they are going even smaller for Wii owners to help out with storage you should be able to fit ~130 songs on one 2GB SD card.  I seriously doubt very many people will need more than one SD card for their Wii.  We're talking about the exception here not the rule.

Even if you were absolutely correct my advice should still take precedence over this issue anyways.  If you have friends buying it on one system you should get it for that system so you can play together, regardless of whether its a bit more expensive or not.  On the other hand if that doesn't settle it then the Wii version is going to have an additional mode that is already getting glowing reviews.  A $7 expenditure that has beneficial uses outside of its GH:WT uses is hardly a reason to write off the Wii version.