I'd go with the C172 - it's probably slightly cheaper, a yoke is representative of the majority of theairliners you want to fly, and you'll find familiarity with a C172 more useful than with a DA40 if, as is highly likely, you end up a flying instructor for a few years hourbuilding.
But it's a minor point, they're both perfectly good training aeroplanes.
As for USA versus Canada - the USA is better recognised worldwide in terms of its licences, but having flown in both environments, I'd say that there's nothing to choose between the two in terms of quality of learning environment. The USA may well offer a better flying rate as somewhere like California will offer more consistently good flying weather than anywhere in Canada.
Realistically if they are both apparently good schools, go with the cheapest. If they're the same, go with the one with better weather.
G