At first I was thinking Miller, but after days mulling this over I say Shaq for a few reasons. First, he causes matchup problems. Take the Lakers for example. Gasol could take advantage of Miller offensively and yet not get exploited on the defensive end. The Lakers just wouldn't have been able to put Gasol on Shaq for more than a few minutes, if that. This would've forced Jackson to go with Bynum for long stretches, despite the knee issues, or go deeper down the bench. We also functioned best when Sheed was in the post and the offense, specifically that second unit, worked from inside out. Doc will have no problems begging Shaq to get in the post. Miller on the other hand just isn't that type of player. He's a face the basket spot up shooter. I think both are poor defenders at this stage in their career when covering the perimeter. However, Shaq is the one that could cause a matchup problem on the other end. Miller is a nice player, but he just doesn't have the offensive tools/physical attributes to give opposing centers problems.
And not a conspiracy type of guy, but how many favorable whistles do you think we would get during the playoffs vs. any non-LeBron led team? One would think Stern would salivate at the ratings a Celtics vs Lakers part 3 would generate along with a Shaq vs Kobe subplot.