Comic-con and Dragon*con have two really different feels/vibes/attitudes/whatever, so it is almost hard to compare them.
Comic-con is almost more "mainstream" at this point, and it gets a lot more industry people, big announcements, and more "current" stars and guests, so it has almost a more professional feel to it, almost like E3 at this point.
Dragon*Con, however, is just about the quintessential party/hang out con. People go to have a good time and enjoy themselves, not to get the latest updates on the industry. As an indication of this, it always seems to be that the people not in costume are in the minority at Dragon*con.