Out of all the teams in the NBA, it's no coincidence that the two teams that are ahead in their series have a bigger front line than their opponents, and in fact have bigger front lines than the rest of the league.
In the NBA size does matter, because of rebounding, defense and scoring. Of course both teams have excellent small forward and guard play, but so do a lot of teams what separates them is the ability to put two 6'11" or taller players on the floor at all times, both starting and with backups.
In both opening games, the Celtics and Lakers were able to blow out their opponents, who couldn't score well enough to stay with them. They got more rebounds and 2nd chance shots, they got more calls going their way and drew more fouls inside on 2 and 1's.
This isn't to say the two losing teams can't come back, but they way they lost suggests that their defeat is inevitable. As for the finals match-up between the two, I give the edge to Boston. LA is a better team than last time, and the Celtics have gone through some changes, but The Celtics have Garnet, Perkins, Wallace and Big Baby Glenn Davis to match up with Gasol, Bynum, Odom and... oops, that's a 4-3 advantage to the Celtics and no-one on the Lakers can handle Big Baby.
Kobe is better than Pierce or Ray Allen, but the two of them together are as good or better than Kobe and the Lakers don't have anyone else with that level of talent. At the point guard spot, Rondo will destroy Fisher on offense and give up points trying to defend him.
Artest adds a little toughness, but it won't make a difference to Wallace, Davis, Garnett or Perkins who are all much bigger players. When push comes to shove, who would win in an fight? The Lakers bigs are big enough to intimidate without playing physical, but Boston is as big and likes to play that way.