I've actually never had problems at the Hyatt, but then again, I generally keep to myself at hotels. I am rather disappointed that they chose the Sheraton of all places, given that A-Kon is in that hotel this year--it will be like a mini A-Kon instead of an AnimeFest, especially with the lack of attendance cap. One of the main reasons I love AFest is -because- it's a smaller, more casual convention. Rumor has it that AFest will be nearly double the size it was last year, and I'm not sure I'm a fan of that. I like having enough room to move around in my cosplay without worrying about bumping into someone like I do A-Kon.
Another difference is that the Hyatt is near a large park area--fantastic for photoshoots, plus a lot of neat architecture is within walking distance. The Sheraton, not so much--the Arts District isn't a good walking distance if you're a cosplayer, and there isn't much in the way of green/natural places to shoot (even the Cancer Plaza isn't exactly natural). Granted, the Sheraton is MUCH more capable of handling large crowds and such, but....grrr.