Based on negative threads here, have never stayed at the Westin. Have stayed at the Sheraton several times though...the sweet sleeper beds are good, the service is spectacular, especially for what you'd expect from a Sheraton in the US. I was pleasantly surprised, although, I did have low expectations, given it's a Sheraton in the middle of Jersey.

Have also seen the Hilton Morristown...definitely go with the Sheraton. Not perfect (the bathrooms are indeed dated, but still function well), but pretty darn good.