he's not really that much better though, if at all
D and rebounding are pretty bad...his PPG is inflated because he's on a crappy team
i doubt this trade would ever happen anyway
He spaces the floor better and doesnt clog the middle like Boozer does. Besides, a lot of Boozers rebounds come as a result of letting his guy get past him and then cleaning up when Noah/Asik/Deng have to contend his mans shot. Once Boozer's crap defense ties up someone else with what should have been his man, he is then freed up to get the rebound on the shot his teammate was forced to contest.
Boozer is also too limited with his height. Remember when he had turf toe and everyone speculated that he lost lift on his jump because of that? Well he still looks the same, more or less.
I think Bargnani can hit shots away from the basket in more ways and is also better at slashing to the basket, which is a better compliment to Noah who is one of the better passing Cs in the league. By keeping congestion out of the lane, it opens up space for Deng, Rose, Noah, and Brewer, all of which are good slashers but run into congestion because Boozer's style of play is one of constantly backing his guy down.
Also, Bargnani is younger and cheaper.