I made the assumption at first that you were strictly talking about quality but you don't mention that. Being an 'eco' guy, and based on what you did write I think you're more weighing the implications of buying something that's possibly shipped overseas a few times before becoming a product, as opposed to something that's made locally.
(link below is no longer valid; it was their page on waterproof/breathables)
...there's a relatively good amount of stuff made in Canada. Who knows where the material came from. Sometimes they tell you where the fabrics originated. In this day and age I think it's great to start rethinking the transport that's involved in the products we buy, if we can. So, given that there are good products available that are made in Canada and if it's MEC you're interested in (because they contribute to the environment as well) and the product is lighter on your wallet, I say go with MEC (or whoever 'made in Canada', provided you're happy with the quality).