Answer to OP's question:
Ellis takes about 22 shots a game (Kobe takes 23).
Curry takes 13 shots a game.
Golden state wants to get rid of Ellis because although he's a valuable player, he's a chucker and he taking way too many shots away from Curry.
Curry is just too good to go underutilized and they can get someone back that probably helps them more than an undersized shooting guard in Ellis.
I'm not the biggest Ellis fan, he dominates the ball and is quite streaky, although with Rondo (who hates to shoot) instead of Curry, Ellis may be a nice addition as a 2 guard if we want to re tool.
Again though, he's probably a bit too short, although he is great because he can run the open floor whilst also being part of a half court offense.