The main advantages of using Transferwise for international money transfers are:
1. Transparency of fees: they charge an explicit visible fee (including a percentage and a small fixed fee), but give you the current mid-rate with no fees hidden in the exchange rate.
2. Funds get deposited in the destination account as a local bank transfer, avoiding excessive holdups and additional fees and taxes that hit international wire transfers in many countries and with many banks.
You won't save any money compared to using traditional forex processors for a simple USD-CAD exchange between your own accounts.