Well, they are both 2 of my top 4 guitarists. I'd say neither can be better. The four best guitarists, in my opinion, are Michael Romeo, John Petrucci, David Gilmour, and Steve Vai.
For vocals, I'd say that Russel Allen is generally better. The situation with Labrie is an odd one. I can't stand his singing in a lot of songs, but I actually think he is very talented. The problem is that he has been asked almost consistently to sing outside of his natural range (maybe he doesn't know his own range, I don't know). I think he is fantastic in the newest DT album, especially on the title track. There were also a couple off of Falling Into Infinity that he was good on (Hollow Years and Anna Lee). Hopefully Six Degrees of Inner Turbulence is a sign of where he will be singing in future releases.
For keyboards... I like Pinnella a whole lot, but I have a major gripe with something. It's his choice of synthesizer. I think his part in the band would sound so much better if he had it set to sound like a real piano, and turned the volume up a little so you could hear it. The sound he has it set to right now is too close to the sound of the guitar from Romeo, and there isn't enough contrast between the two instruments sometimes.
But I think DT wins on drums and bass. It is strange, because I think that the over-all technical talent of DT may be a little higher than S-X, but S-X's songs are so much more interesting.