I would say Park Hyatt>King Eddy>Westin>Sheraton for the hotels in the chains you mentioned. The only thing about the Westin, is while it is on the Harbourfront area, it is a bit isolated from the city, so walking will be a bit more. The others are very central and will be walkable as well as close to streetcars and subways. If you consider other hotels, I might thrown in Hotel Le Germain, which is a nice boutique hotel in the King West area.