China's - they have more labor (workers to ride the backs of...tax, etc) and assets (land, etc) to back their currency than any other country in the world. This will probably start to play out in a very short time and I see no one stopping them.
Canadian dollar is in good shape, balanced budgets, trade surplus, low unemployment, commodities based economy, foods, lumber, oil and gas, remember we are going through the commodity boom globally.