Beasley is just as much as a volume shooter as Bargnani and connects a better rate (49% vs. 44%). Plus he rebounds better and is better defensively.
The main point is... Toronto is bereft of talent and as much as you want to knock Beasley, he was a number 2 overall pick and 21. To sit there and say that he can't get it together when we've seen other players get their s--t together when they start off with shady reps (Zach Randolph and Carmelo Anthony to name 2) is just jumping the gun. Klieza is what he is (as Tim W. described, a good role player). Beasley has way more upside. By the time that the Raptors are good, Klieza might not be even with the team. Why not take a chance on a young guy who seems to be a decent kid that just has some issues that a lot of dudes I grew up had and kicked when they grew up? If it doesn't work, oh well, you lose 60 games either way.