I have been to conventions in SF and had the so-called shuttle service be so poor that we had to take cabs. Sooo, I recommend you select a hotel near the convention center and I think everyone is too hard on the Marriott. I was very happy there as a Gold member. The bar up top is fun. The Sheraton is wonderful for atmosphere but I have never stayed there. Certainly, the Sunday Brunch is a treat visually and gastronomically.