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?