Perkins vs. Wallace - edge to Wallace, but only if he's shooting well from outside. If Perkins can outrebound him and clog the lane on the help defense, he's done his job.
I actually think Wallace is a more effective player when his shot isn't going and he has to get down in the blocks to score. He has an unstoppable turnaround in the post, keeping the ball up high and kissing it off the glass. Not even Shaq could stop him when Sheed caught the ball in good position back in that Blazers/Lakers series a few years back.
I've never been a big proponent of comparing matchups by position, though its a fun exercise, primarily because it's more about how each guy accepts and performs his role than how talented he is relative to his counterpart.
That said, I predicted the Pistons in 5 earlier. As talented as the Celtics are, they let the worst team in the playoffs (and a team that would have finished in 12th place in the West take them to game 7. Cleveland is a better team, but even when LeBron struggled the Celts couldn't take advantage and let the Cavs stay in the series. I think Detroit is just a more battle tested team and knows how to win when it counts. Not to mention that the Pistons were leaders in the regular season in terms of fewest turnovers while the Celtics (I believe) averaged more per game than almost any other playoff team.
He'll be a key factor this series.