To me this depends on what you want to get out of going to a convention, and your personality type.
It is helpful to identify if you're going for exposure, to network with models, to have fun/experience camming community, learn about the industry, shoot vids, cam with other ladies, meet new members, meet your current regs and spend time with them, or any combination?
NJ EXXXOTICA - Huge amounts of members make it out to this one for me. I think just cos so many ppl live near this location. However, if you're going to party... it's like an hour out of NYC and it's in kind of a strange location. This past year had really huge crowds.
Vegas is the biggest one. However it's also ... THE BIGGEST ONE. If you're easily overwhelmed or want to try a smaller convention first... do an exxotica.
The other exxoticas i can't comment on cos i haven't been to them. I miss the ones they'd do down south..
There's also cammingcon in miami i believe.. but i've never been to that.