Arnold Myint Restaurants
I've been to all three, and they are all good. Which one to pick really depends most on which menu appeals to you the most. The atmospheres are different, too -- ChaChah, while casual, is the most sleek. PM is a little shabby around the edges. Suzy Wong's is more whimsical.
Of the three I'd usually pick ChaChah, but really it would depend on my mood at the time. ChaChah runs some great specials, esp for happy hour. It would be worth your while to Like them on FaceBook or follow them on Twitter as they post frequently about specials that day.