SDCC is the grandaddy of all cons for sure. I run a small LGBT press house and we do pretty decent at SDCC mainly because they offer juried, low-cost tables for Small Press! Supporting the middle-level comic vendor is a dream come true. But - and here comes the but - you have to plan carefully for this show to do well. You have to submit your actual printed in the last 12 months comic to a jury for selection. Comics has to be your primary business focus! If you mostly sell plush dolls and have one tiny comic book for them to comply with the rules, you won't be accepted anymore. And the artists alley is primarily for original comic book working artists - no fan arts! If fan art is your primary business, be prepared to go up against HUGE BOOTH purveyors of professional level high quality poster and mounted wall hanging fanart. SDCC is NOT a place to sell little prints. UNLESS the work is highly unique and 100% original.
And originality sells at Comic Con Small Press area as long as it shines and has a distinct unique look/feel/message. If you come in with a big sloppy stack of poorly executed cheap looking Kinkos zombie comic books and no signage or marketing tools, be prepared to flush the $500 booth cost, $250 parking and $1200 hotel bill down the toilet. If people want another friggin zombie comic, they can walk two rows over to the actual WALKING DEAD booth with the enitre cast. You have to be competitive. Be unique. Represent yourself well and BE ORIGINAL. Then, its' the best comic show in the USA - hands down!