As far as the Twilight autographs for Comic Con are concerned. It seems to be very disorganized and their is no guarantee you would even get an autograph being it is done by raffle.
Plus last year
Jen aka dreamer4ever and I tried to get autographs for Supernatural and it was a mod the place and very disorganized.
I would much rather go to the panel and see clips from the movie as well as see the cast interact with one another and see the author of Twlight Stephanie Meyer and the director Catherine Hardwicke talk about the book and movie.
Up to you if you want to wait in line for the Autographs at 9:30 in the morning but we are going to the panel!