Andersen is going to help the Celtics, if signed. His strenght on the offensive end is in rebounding and dunking the ball. Who would you rather have on the other end of KG passes, him, or some slow guy who takes forever to gather and get a possible dunk attempt.
Who cares about dunks? We're not playing the Harlem Globetrotters. I only like dunks because they're an efficient way to score, but you have to be in position to dunk and that increases the risk of charges and TOs. Andersen is not a very efficient scorer for a guy who mostly dunks (0.466 %FG plus .601 %FT, combining lower than Pollard, Perkins and PJ), so I can't see his strength.
He is a good rebounder, but he doesn't help the team much in the def. rebound and that's what we need from our backup center.
Answering your question, I rather have the guy who gives me solid post defense and good screens, not the dunker.
Also, nobody answers this: Why haven't the Hornets offered him a new contract?