I know this has been debated time and again on here, but after watching the DVD, I think both sides of the argument are correct. One-on-one, Mace is clearly the better of the two, and pretty much bests Palpy in the saber duel. However, he doesn't take the opportunity to kill him when he has it, now giving Palpatine the edge. Once Anakin arrives, it's clear from Palpatine's facial expressions that he's throwing the fight to see what happens next.
Speaking of Palpatine, thanks to the pause button, I'm now convinced that he was, in fact, looking at the Death Star plans when Anakin walks into his office a few scenes earlier.