I am currently living in Brazil and planning to move on 1Q2018 to Canada.
As in Canada there are BTCs ATMs, can someone tells me if it is better to exchange my BRLs to BTCs instead of CADs?
Check the exchange rate between your local Brazil exchange and one you could use in Canada. Whom ever has the best rate should be the one you use. However you'd also have to exchange your reals for CAD.
Don't bother with the ATMs, their exchange rates are really, really awful. They aren't even close to competitive and the convenience isn't worth it.