Lamar Odom is good enough to be a starter on just about any team in the league.
In fact, I'd say he's better than Ariza. Phil Jackson knows what he's doing though and he wants some fire power off the bench. Lamar Odom gets the minutes of a starter and they are well-deserved.
Also off the bench for the Lakers you have Luke Walton, Shannon Brown, and Jordan Farmar.
For the Magic you don't see too much. JJ Reddick got off to a hot start early on in the playoffs but since then has hit a cold streak and is back to his normal self.
Although he can and probably will come in and drain some deep buckets for the Magic, he won't be much of a factor. Surprisingly, Marcin Gortat has done a great job backing Dwight Howard up and I think he'll do OK in this series.