I like to look at it like this: LHW division - Chuck Liddell was UFC's LHW Champ, UFC's poster boy, and the main fighter held responsible for the UFC's rise. He fought 3 LHW's who came from Pride, he lost to 2 of them via KO1 and beat 1 via closely fought decision. Rampage took the belt when he KO'd Chuck, and Rua went on to win the belt after he KO'd Chuck, by knocking out the man who the UFC was hoping would be the new dominant LHW.
Any non-stylistic advantages you could think of went on Chuck's side - cage experience, cage tactics, crowd support, how the UFC works, knowing people within the company well etc, and he still lost brutally. Those are factors because they may have been taken for granted by guys like Liddell, but not having those things would have had an effect on the Pride guys, they were expected to make a big explosion with very little dynamite. I'm a Chuck fan and think he was that good, and I don't know how the 'Pride fighers aren't good' argument stands when you look at his record against them.
Just looking at one division is slightly narrow minded, but it encompasses 3 of the main 5 Pride fighters who did well in UFC. 4 if you count Hendo obtaining the Strikeforce LHW belt.