all games are not created equal

This is purely based on controllers.

The guitar controller on Rock Band is MUCH more comfortable and practical than the GH:WT or GH5 controller.  The fret buttons take up the FULL FRET, as opposed to the childish smaller buttons on the GH controller.
The strum bar is a matter of preference.  RB's is completely silent, but it's also a little tougher to be precise on fast patterns.  GH's is still clicky, but it's fairly quiet and you barely hear it if you crank your sound up as much as I do, and it's perfect for fast patterns.

I much much MUCH prefer the solo buttons over GH's slider.  The slider just isn't implemented well.  Transitioning from the normal buttons to the slider is just terrible and pointless.  You might as well just stay on the buttons the entire time.  However, with RB's solo buttons, I can transfer there and back with ease.  They're smaller, so there's less finger movement, and I can feel where the buttons are when I play.

As for the drums, again, it's a matter of preference.  The kick pedal is far superior in RB, IMO.  I'll give GH credit for having cymbals a part of the base installation, and the pads are quieter, but otherwise I once again prefer the RB drums.
I have the three cymbal expansion for RB, and I love 'em.  It makes it really satisfying to roll the snare, toms, and then finish with a cymbal crash.  Plus in free play, you pretty much have an entire drum kit, so you should be able to play any song you want :)

Vocals... eh whats there to say.  Who plays vocals?

The more I've been playing these games, the more I enjoy playing GH series over Rock Band 2.

 

First of all the gameplay is exactly the same with main difference in how the notes look.  They both have some fun songs to play and some not so fun songs.  But what makes GH better is how the story takes you through ALL the songs throughout your career.  While Rock Band's Tour mode keeps on making you play some songs over and over even when you've unlocked and moved on to different venues!  That's a crappy way to rob players of more gaming hours.

 

RB does have a very comprehensive list of songs but why recycle them!?  If I want to play the song again I would simply just go to Quickplay mode and rock.  Also if you are playing RB for the first time, I noticed that it doesn't let you play any song right away when you go to Quickplay mode.  You have to unlock them in Tour mode.

 

I do like how RB will highlight a song's guitar solo to earn more points but the novelty wears off after a few songs.

 

Overall I enjoy playing through GH because it just flows through all the songs.  It keeps things fresh with less of "UGH!  WTF!  I just played this song!".