I got into NPSIA and GPSIA as well, but will be going to Munk. Actually, the friend that I was mentioning just got recruited into DFATD. So, in response to the previous poster, I would say that there is clearly more than one way to get into the Canadian Foreign Service (if that is your ultimate end goal). I am personal more interested in international opportunities with multilateral organizations, and have found that NPSIA graduates typically focus within the Canadian market. I also liked the fact that they had a lot more international students in the program, who have all mentioned that the University of Toronto name is well-recognized beyond Canada's borders. In the case of networking, I wouldn't underestimate what Toronto has to offer as well. Ottawa may be the nation's capital, but Toronto, in my humble opinion, the far more exciting place to live, and has a lot to offer if you are concerned about the 'networking' aspects and very internationally orientated.
I personally don't believe that you won't be making a bad choice wherever you go. Although, I thought that I should probably do my part to balance out the conversation. I have another friend that recently got into the School of Public Policy and Administration at Carleton, which offers the MA in Public Administration, who has also mentioned that NPSIA students (of course, not all) have had the reputation of being arrogant and even borderline entitled. Again, I would mention again that co-op opportunities in the government are not as plentiful as it once as and much more competitive to come by.
Just my two cents, but I would like to hear what you all think.