Hi there,
This all depends on your views towards currency.
If you hold U.S. stocks and the USD rises in value relative to the CAD, you will benefit in terms of higher returns. Conversely, if the CAD rises and the USD falls, it has the opposite effect and your returns will be negatively impacted. In general, when the CAD rises against the USD (or other foreign currency), ETF's that are hedged tend to win out. When the USD (or other foreign currency) rises against the CAD, unhedged delivers better returns.
Personally, I tend to avoid hedge products. For starters they aren't an exact science and secondly, they are more volatile. There is also the risk of trying to switch back and forth which means what? Market timing. Investors are unlikely to time it correctly and could potentially lose out. There is also evidence to support the hedging provides limited benefit over the long-term. Not saying that buying hedged is a bad idea, but it is not something that I am particularly interested in.
Mat