Leake for Choo is a "loss" on the value front straight up in my opinion, due to the years and money. However, it makes the Reds a markedly better team in 2012, assuming his defensive performance (as measured by UZR) was an abberation. If there's a reasonable chance he can be resigned/extended as some point prior to hitting the FA market, I'd be game. If it were just a 1 year rental, I'd be more inclined to go the prospect route.
I would certainly not, however, trade Leake and Cigrani and more for Choo unless he was signing an extension the day he landed in Cincinnati.