When I was applying in the last cycle, I was told that the MPP program at U of T was not mature enough (i.e. the school was still figuring out how best to structure the program). I was also told that Carleton was relatively more connected with the federal government, Queen's with Government of Ontario, and Ryerson with City of Toronto. So, in addition to school rankings, it might also be helpful to think about which policy areas or jurisdictions that you would like to work for. For example, if you are interested in social policy, which falls mostly in provincial jurisdiction, you probably wouldn't want to work in Government of Canada, in which case Carleton would be less appealing than Queen's, and vice versa.