I think the broad generalization is that for this particular class and kind of international institution, the pluri-lateral summit institutions, the larger the number of members--such as the APEC leaders meeting in 1997 in Vancouver, the Summit of the Americas, with 34 leaders, in Quebec City in April 2001, and of course the G-20 in Toronto--the tendency is, for I think understandable reasons, that they have to be held in larger cities.
But for the smaller G-8, the tendency, and perhaps the Canadian tradition, has been to hold them in smaller resort-like settings, in part given the unique advantage of having the event leaders looking each other in the face, relaxing, realizing they're all in it together, and interacting as human beings, rather than reading speeches at each other, which can come alive as it did at Deerhurst.
The Canadian tradition, of course, was set by the Right Honourable Pierre Trudeau in 1981. He had the choice of hosting Canada's first what was then a G-7 summit just in Ottawa, in the capital city, but said no, that he wanted to share it. He wanted to do a significant portion of it in Montebello, Quebec, despite some of the known disadvantages the dual hosting would bring.
So the smaller the communities, the bigger the benefits. The historic Halifax summit of 1995 was held in the largest of the smallest communities, but the Canadian tradition does go back to Pierre Trudeau in 1981.