Rockband 2 or Guitar Hero World Tour?

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Currently I have the first 2 Guitar Hero games for PS2. I own Rockband and Rockband 2 for Xbox 360 and Guitar Hero 3 for Xbox 360 as well. I am not sure about purchasing Guitar Hero World Tour. Is it worth it? I have considered the downloadable content for World Tour and I really like what Rockband 2 has. Is the game play any better? Tell me why you like one or the other better? And for those who have both do you play one more than the other!? Thanks