Farpoint is really small, and has gotten smaller over the years. I don't bother going to it anymore (though I probably would if they started courting the fan groups to set up displays and demos more). Shevacon is the one I go to at this time of year (first weekend of march, down in Roanoke VA). It's just as tiny, but they really like the fan clubs, and the droid group gets treated well, so we go.
Shore Leave is the Baltimore one I still go to. It's quite a bit bigger than Farpoint. There are some huge ones out there too, but they're usually farther away.
Dragoncon is one of the bigger SciFi/Fantasy cons around, but it's down in Atlanta. They take over 3 large convention hotels. Never been to it, but I'd like to at some point.