Mandarin is much better (to make a direct comparison). Why you ask...well for starters I have been to Imperial twice and both times half of the food trays are empty limiting selection. Furthermore the food is better at Mandarin. My favourite item at buffets is torpedo shrimp. Unfortunately at Imperial its over-battered and you can't taste the shrimp. The hot meal section is definitely the highlight here. Though when you want desert you can choose from some normal ice cream flavours, which is fine but Mandarin has the options to make a delicious sundae. Imperial is not a particularly terrible place, but drive 10 minutes to Mandarin on Kingston Road to enjoy a far better Chinese buffet.