I tried the SOTP once but the Westin just keeps me coming back. None of this crazy zoo you mentioned - the lounge is truly first class & breakfast & evening drinks are always fantastic. The same person's been there for 5 years and still recognizes me after a year of being away!
It's one of my top homes away from home. Shangri-la is a bit of a concrete dump IMHO. Check out this review from the other day...
http://www.theage.com.au/travel/a-ni...1127-6j55.html