John Petrucci vs. Michael Romeo: whos the better singer?

Where did MJR do backing vocals? I saw him credited once, and meant to ask the question, but I've kept forgetting.

And Pinnella, for that matter. Didn't he, as well?
 
Romeo, petrucci is kind of shit especially when he tries to do falsetto its always out of tune. When hes singing normally it sounds like country. Portnoy is a good backing vocalist though. Personally I don't really think it matters if backing singers are crap though, it adds to the live feel and sometimes its funny; steve harris being a good example.
 
So do Romeo and Pinnella do this live only? Because I thought I saw credits on Twilight for backing vox. When did they do that?