We live in Mississauga and both work downtown in T.O.
Depending on where you & your spouse work will have a big impact on where you choose to live.
Personally I would choose to live as close to work as possible to cut down on commuting time.
As for schools etc. BitsnBearsMom said it well it depends where you choose to live. Each city has great areas to live and some neighborhoods that are not as appealing.
Guelph is a good choice lots of great areas, nice downtown, the best in my opinion of the area of Kitcherner, Waterloo & Cambridge.
With that said if I was working in the north end of Waterloo I would like to be close to work.
Just as I would not look forward to driving into Mississauga or Toronto every day from Guelph.
OP we need more info.