Haha, this thread is asking for a fight. Most have their own redeeming qualities, and a lot varies on personal taste. I really don't care for small cons, and all of my bad con experience have been at them. Some people I know love them. The same people I take to PAX East wouldn't go to Otakon if I paid them, and vice versa. I personally tend to enjoy any well run large anime or video game convention, but I'd have a hard time picking a favorite. PAX East and Otakon top my list, but I've certainly enjoyed AB and a few others as well.
"The important thing is no one was hurt... No one who counts."