Alright here's some pros and cons to this scenario:
Calderon is a better PG offensively than anything we've got.
Bargnani is a good fit next to Andrew Bynum.
Calderon's contract turns into a big 10 million dollar expiring next season
Calderon is awful defensively, worse even than Fisher/Morris/Goudelock.
Bargnani is a volume scorer and would not get the same opportunities he does in Toronto.
Bargnani's contract runs until the end 2015, which puts the Lakers in a terrible financial position.
The team's rebounding and passing ability plummets.
The team's defense suffers.
Bargnani is a volume shooter, he puts up over 17 shots per game easily leading his team in attempts (next is Derozan with 13.7). Kobe shoots over 24 times a game on average this season, which eats into Bargnani's attempts. Andrew Bynum averages around 12 shots per game which eats into Bargnani's attempts. Gasol shoots only about 13 times a game on this team and Bargnani would likely shoot less. He'd come here as the third option and would be less effective scoring the ball.
Not to mention he averages only 6.4 rebounds a game at a legitimate 7 feet tall. That's pathetic. Kobe averages 5.7 so Bargnani gets less than a rebound more than him a game. That's horrid. Gasol averages 9.4 by contrast.
The positive out of this would not be Bargnani, who fits less ideally than he does in theory, but Calderon. He's a very good passer and can be effective with the ball in his hands. However, his positive impact is also weighed against Kobe's position on the team. Steve Blake is a decent PG (not anywhere near Calderon, but decent) and his numbers are limited by what Kobe does to the offense; namely take possession of the ball in half court sets.
In short, the trade doesn't really make this team much better. Unless Toronto would also be willing to give up some picks and prospects then I don't see this as a positive move at this point in the season.
Stu : "Yeah, that's an old fashioned whoopin'."