I've attended both ( also I'm attending both this year) , I feel for cosplaying Anime Expo is the better con. I only attend the convention for friends, but I feel I pay way too much money and received less than what I deserved every time I go. The only events they have that I enjoy greatly are the dances. I lives 15mins away from Comic Con and it was my first con, its more geared towards comics and I've seen some wonderful cosplays there as well. Though I find comic con to be more of a media con, meaning whoever has the most money will be given a spots. They hold all sorts of panels, but getting into one due to the lines can be a real pain. I enjoy the high amounts of swag though, it seems everyone gives out stuff for free, so you hardly need to spend money to walk away with some pretty neat stuff. Tons of big name stars come every year, and you can get a tastes of the newest games coming out. I feel happier, and enjoy my time more at comic con personally.

Hope that helps