I stayed at the Westin, the Sheraton Premiere, the Marriott, and the Hilton, on an alternating basis, for 7 months (gotta love/hate those per-stay promos). 110-ish nights total, so I got a pretty good sense of each property.
The Westin would be my last choice of the four.
See
http://www.flyertalk.com/forum/showthread.php?t=700283