Was there any difference between the 6 Pains, besides their abilities? I know that every Pain used a different technique, but I'm interested in knowing if there was any difference between them besides their abilities?
To be honest, I felt that the way a ninja uses and handles his/her power makes them stronger. I really can't comment whether there were any difference of power among the six Rinnegan users.

Why do I say this?

Recall the incident between Sasuke and Itachi's fight. Sasuke used his Sharingan very efficiently when he fought against Itachi.

So bottom line: it totally depends on how a wielder wields the weapon.