Funny, I have stayed at both hotels on many occasions. I always try to avoid the Westin. I much prefer the location of the Sheraton and I have never received an upgrade at the Westin besides a lakeview room.
While my upgrade success at the Sheraton is not great, I did many years ago as SPG Gold - get upgraded to a jacuzzi suite.
In terms of rooms, I found that both hotels have rooms that are dated, but felt that the Westin rooms were even more dated. Go figure.