I don't trust Boozer. The only reason why I wanted him on the Jazz this past year was because he was in a contract year and had to perform to get the contract. Now that he has it, he'll be the boozer that Jazz fans grew to hate. He'll miss games, play no defense, talk a lot, and generally just not be worth the big money.
Jefferson is a bit of an unknown, but there is major potential there.
Since Jefferson is bigger and taller, he gives the jazz many more options.