If I have to pick a place in plaza that I have to eat there for a semester I would go for SOGO. Their food is just too good, especially the Hunan rice noodle( trust me, add a fried egg to it). Also the Chinese style crepe is also awesome and the grilled lamb!
After my 4 years in Waterloo, I must say that one of my favourite restaurants in the plaza is Sogo. I have only have the noodles dishes but they are delicious every time - either lamb or the pork. If you like a little kick, say yes to spicy! Overall, for the price you are paying, you are getting a decent amount of food. I opt for the small noodles but the large size ifs maybe $1-2 more and is well worth it if you have a bigger appetite. I have also seen popular dishes thee being the crepe and if you are looking to spend more, they have lamb shanks that are seasonally priced. Although this might not be the most fancy place, it is definitely super authentic and is a place that keeps you coming back for more.
Sogo's meat to rice/noodle ratio is way lower than other Chinese restaurants in the plaza. Expect something like 5:1 meat to rice/noodle ratio for your dish. Their prices are fair however and the food is very tasty and authentic. 4 stars mainly for their Chinese street-style foods. Always made fresh on the spot, their Chinese crepe brings me back to my China days. They are also one of the few places that has fresh soy milk.