I only own the RB2 Wii version, but the gameplay is still the same across all the platforms. And there ARE some integral differences in ACTUAL gameplay mechanics across GHWT and RB2. Namely, in GHWT, everyone shares Star Power, and must activate it individually to get the full multiplier going, and the drums/vocals can activate Star Power whenever they want. However, RB2 gives everyone their OWN Overdrive bar (same thing as Star Power) which can be activated to create a multiplier, but the opportunity isn’t wasted if everyone doesn’t activate. At the same time, Drums and Vocals must wait for specified cues to activate their Overdrive…
Songs… * shrug * Honestly, I like the songs from both games, and I believe that the games have been patched to accept both sets of instruments. I could be wrong… Anyway, get whatever version’s full instrument pack (You WILL need to get a 2nd guitar separately for both versions, though GHWT does offer a 2 guitar pack, but then you need to buy a USB mic and drums separately…) But whichever version you get, they’re both excellent experiences. Wikipedia has song lists for the songs on the disks AND downloadable content. Let that be your guide as to which game you want if it matters to you.