Playing the game
There's a fundamental difference in the ways "Guitar Hero World Tour" and "Rock Band 2" play out: One punishes you, while the other is all about the music. Let me explain.
'Rock Band 2': If you were to buy the game, plug everything in and throw a party, you'd have all of the songs waiting for you and ready to roll. If you plan on hosting a few of your less-talented buddies, you can resort to No-Fail Mode, which lets everyone blast away regardless of how off-key the playing is. In short, though plenty of challenges are available for the serious gamer, you can also flip a switch and just have fun. Crazy idea, eh?
'Guitar Hero World Tour': With this game you need to unlock all of the songs you want to hear. So, if you plan to throw a "Guitar Hero" party at your house, you'll need to make sure to hold a marathon jam session ahead of time to unlock all of the songs. Arguably, performing that initial step gives players a sense of accomplishment -- a feeling that they've won the fight for their right to rock. But what about songs you don't like or don't want to play through? To unlock more of the music you want, you have to take the bad with the good.
Rock Band can't claim the high ground here, not after the first game. Harmonix carried their policy from Guitar Hero II of making some songs inaccessible to people who play on Easy.
Ultimately, people who play on easy and people who play on expert both paid their £39.99. I'm glad to see Rock Band 2 has corrected this.