I've been to the last... 4
San Diego Comic Cons, and 1
Botcon. Botcon was nice enough, but I didn't care for many of the panels they had that year, and Botcon's exclusives are hideously overpriced. (Of course, to be fair, my back had just gone out prior to Botcon, so my skipping of many panels might have more to do with that, rather than the content.)
I have considered going to
New York Comic Con instead of SDCC, seeing as how I live on the East coast, and SDCC is on the west. (Plus, after SDCC, I've heard that NYCC is the 2nd largest con.)
The reason why I keep hitting SDCC, is that there's always more than a few panels I enjoy seeing (assuming I can get into the room).. There's more than a few premiere showings of some straight to DVD stuff.. The exclusives are always interesting, and sometimes even worth buying.. Plus, there's a butt ton of freebies to be had, I'm disappointed if I don't manage to snag at least 6 t-shirts, 1 convention bag & maybe a DVD or 2.
My suggestion to picking a Con is always to look at the kind of panels they get, at least look at the prior year, as you won't likely know everything before they sell out of tickets. You might like the theme behind the con (like Anime), but if its just showing movies you can rent/already own, plus costume play... Well that's a waste of your time & money.
SWB