Local cons - I haven't had the opportunity to do international cons (... yet. Seriously considering Thought Bubble in the UK at some point. We'll see.) I've done two different types of cons - the big anime-con, and the smaller, comics-only con with a focus on self-publishing/small press.
I do best at the small-press cons for obvious reasons - I don't sell fanart, and my art style doesn't fit immediately into the archetypical "manga"-look (there are manga influences, but yeah), and people coming to the small-press cons are looking for small-press comics and original art, mostly. It's also a good place to make friends in the business and talk to publishers and stuff - though I still have to work up a bit more courage to that properly! - and while I don't sell out of stuff, I usually do pretty well. I've been able to cover my tabling and printing costs with a bit left over - which, considering how tiny a pond the Swedish comics-scene is, is pretty great!
I did okay at the big anime-con, too - I covered my tabling and ticket cost, if only just, and managed to talk a good enough sales pitch at the anime-fans that came to my table almost always went away with my original comics in their pockets. I also consider it a great success considering the fact that the weather was terrible, the tent we were in was leaking rainwater, the layout of the Artist Alley was pretty terrible and I had just about the worst placement in it.
But yeah. If you sell original stuff (which you kind of should - selling fanworks is a very murky legal area, and should be avoided if possible), you are likely to do better at cons that are geared towards that. They'll market themselves that way, and will therefore be getting a crowd intent on buying original works - so you'll have to spend less time convincing people that your original work is worth their time.