Choptliva is right -- the hotels are geographically close, but feel quite far apart.

The area immediately around the Sheraton can be desolate on weekend thanks to the fact that the property is bound by the Vine Street Expressway to the north, parking lots to the east and west, and a school to the south. There's just not a lot of foot traffic around the Sheraton. Hopefully that will change as the northern part of Center City continues to fill in; perhaps the (ill-conceived but underway) Pennsylvania Convention Center expansion will help move that process along.

By comparison, the Westin is smack in the middle of Center City in Liberty Place and surrounded by shops and apartments. There's much more activity in the immediate area both during the week and weekends.

As for the Sheraton itself, I've stayed there a number of times before moving to Philadelphia (both when it was a Wyndham and a Sheraton) and put relatives coming to visit there. It's a perfectly adequate hotel. It's by no means my first choice of city hotels (Starwood or otherwise), but when the rate is low, it's perfectly acceptable. The views can be terrific, the rooms are generally spacious with some clunkers out there. I find the staff typically Philadelphian (yeah, that's probably not a complement). My worst experience there has been with the elevators -- when there's a large group coming and going at the same time, such as for events in the ballroom, they can be painfully slow and packed.