I think you have hit the nail on the head there.  If you've looked at the PS3's lineup, and the Wii's lineup, and already decided that the Wii's lineup is more fun, you're probably going to be happier with a Wii.  Obviously if movies factor in, you have to consider that the PS3 is a great Blu-Ray and DVD player, and the Wii isn't.

I think its pretty fair to assume that future games on both consoles are going to be in the same vein as they currently are, though.

Well I would say that your Rockband experience will be better on a PS3.   (That's just my opinion). (Better graphics, Audio, Easy access to Downloadable Content, Better online network,  Free online gaming).    But you said you liked the 'Wii' games better?  Rockband is just one of many games.  How avid of a Rockband player are you?

Could you elaborate?

The gaming experience the two systems offer is wayyyyyy different.

I'd get the system you would have the most fun playing games on.

If your buying a whole system mainly for one game you should just get the cheaper system seriously.

 yes you r my friend, just joking but y would graphics matter in rockband

well there are loads of other games i like on the wii, like mario party and that stuff. i really like guitar hero too. but what really makes me want to get a console is the fact that there is a beatles version of rockband coming out..... so thats my main reason for getting one. but thinking longterm, the ps3 is more advanced and maybe it has hidden advantages

I don't think you should take anyone else's opinion at all. =)  Sounds like you have a tough decision ahead.  Wii + games you are definately looking forward to.... or PS3 with better RB experience, great movies, and gaming you'll have to explore some to find stuff you enjoy?

Tough choice.  I am weak in such situations.  I bought both.

Other than Rockband... what games will you be wanting?

In my opinion, graphics for a game like Rockband hardly matter. Rockband is all about the supurb audio and gameplay.

The PS3 does (apparently) have an advantage in the audio and online departments, so weight up how important those factors are for you in comparison to the price difference.

Most importantly though, as I'm sure you wont just be playing Rockband alone, take a look at the present and future game library's both systems have on offer.

You have already mentioned that you think you might prefer the Wii's library. If you're certain about that, I think the Wii is the choice for you.

Honestly,  the PS3 has more extra features than the Wii.  (Blu-Ray, Larger Hard Drive, etc)  but  by the way it sounds you really like what the Wii has to offer in terms of games. (Mario games, etc).    You should probably get a Wii.  Graphics won't really matter for Rockband anyways and you'll get to play all of your favorite games or games that interest you like Mario Party.

I would only consider getting a PS3,  If you believe you're going to have the desire to play some of their better games (Little Big Planet, Uncharted, Kill Zone 2, Metal Gear Solid 4,  Gran Turismo 5, God of War III, etc)  and/or you really want to watch High Definition movies,   OR you are just a really big graphics guy. (Which the PS3 clearly has the advantage over the Wii in that regard).

What I would suggest?   Just to make sure you're making the right decision in your eyes.  Investigate some of those games I  listed above (Little Big Planet, Uncharted, Kill Zone 2, Metal Gear Solid 4, Gran  Turismo 5, God of War III)    if they interest you more than the Wii games?   You might have found your choice.   

If you're really not too enthralled with anything you see above?  I would certainly go for a Wii.  It's cheaper, it will provide you a fun time regardless of graphics and as you said games you enjoy are on the Wii.   Rockband will be as well.

**EDIT**

And assuming you've seen many games which the Wii has to offer?  But don't really know what the PS3 would provide you?  These are just some videos of the best current/exciting upcoming games for the PS3 IMHO.   If these aren't really your thing?  100% go for the Wii.    Just do your research and I'm sure you'll be happy with either choice.

Little Big Planet

Uncharted : Drakes Fortune

Kill Zone 2

Metal Gear Solid 4

Gran Turismo 5  (Not released yet, Looking like early 2010)

God of War III   (Not released yet, Looking like early 2010)