Differences between schools: cost (i.e. Dalhousie is very expensive), theoritical vs. practical training (not sure which school is which, sorry).
Does it matter? Yes and no. I went to McGill and found a lot of busy work and some useful courses. It's more like an introduction to running a library. The real learning comes from actually working in that environment. I suggest you get part-time work in the field you're interested in, whether it's a library or archive or whatever.
It's very hard to compare library schools. Time and time again I hear people saying to compare cost of the programs, as the end result (the MLIS) is comparable. Good luck to you!!!