SDCC it's a huge media event. It's loud and very crowded. Artist Alley is stuck off to the side of the immense hall and the tables are pretty much freestanding. It's hard to be seen and make a statement when the crowd is high. Unless you have a banner stand, the banner hanging from your table will be nearly invisible. The majority of the artists are comic based. The attendees are cartoon coloring pages lovers, but are increasingly more interested in the lifestyle entertainment companies. Artists in attendance range from aspiring to the rock stars in the industry, the rocks stars tend to have booths rather than tables in the alley though. Prints and portfolio books are the principle sellers. There are a decent number of art directors on hand, and the companies are quite varied, from publishers to digital game companies.
IlluxCon it's a small, intimate event that features the best fantasy and sci-fi artists. It is very low key and sedate and offers lots of face time with the attendees and the artists. The entire event is focused on the artists. 99% of the space is dedicated to the artists. The attendees are a mix of f/sf art fans and collectors. Artists attending fall into three categories. The top 50 are in the main hall. This is a veritable who's who list of s/sf art. The show case is a mix of working artists, up and coming artists and a sprinkle of high caliber students. Sales tend to fall into two categories: Collectors are usually looking for high quality originals. Fans are looking for prints, portfolio books, lower cost originals and sketches. While there are no companies in attendance, there are a growing list of top tier art directors from publishing and digital game companies (Blizzard, Rock Star, Naughty Dog, Wizards of the Coast, Paizo, and more). As you can see these two events are really different, and you'd be sitting on the sidelines wondering why other tables are killing you in sales (even by lesser artists) if you don't tailor your presentation and offerings for the different crowds.