Actually they're about the same. The ony reason GH was considered harder is because they'd either over-chart things (chords instead of single notes) or have a run on notes too quick for medium players to keep up with. Nowadays, they're about the same, except Rock Band has the 4th and 5th button on all difficulties now.

Cool. Expert FCs? I have 130 expert FCs between GH3, GH:Metallica and GH5.Just a bit. I have ~100 FC's across the games, including Rock Band, and can play expert level on all instruments.

Get Rock Band 3 then! Even on easy it introduces the other buttons. Only something like 1 - 5 per track so it's not silly but gets you into the groove

I started with GH3 and would kill to play Freebird but alas, if I go back to GH3 and even World Tour now, I find them so unplayable because of the angle of the board and the crappy gems. GH2 would be 10x worse.

Rock Band 3 has Freebird
(also lots of other cool stuff!)
 
	