I stayed at the Westin and the Ritz about 4-5 years ago and loved them both. The Westin is really nice and their lounge was also very nice with great staff. Very noveau.
The Ritz was older and much more classic. A much better and a much more spacious club lounge with food presentation five times a day. Again, great staff.

You can't go wrong with either, so whichever gets you a better deal and a lounge access would be my suggestion..