They should be close, assuming you can actually find an ATM that will give you free withdrawals from BoA. Keep in mind that exchange rates can also fluctuate intraday, which makes it even harder to know exactly which payment method is ideal at any one time (on a particularly volatile USD/Hungarian Forint day in March, I had the exchange rates on purchases made on the same day vary by over 1% on my Cap1 statement). But I'd try to do most of my spending with the Cap1 card, because you don't have to worry about ending up with unspent CAD cash.

You might find the wiki that goes with this thread helpful:

http://flyerguide.com/wiki/index.php...reign_Exchange