A few weeks ago, we came back from Milan via YYZ on an AC flight, and we had to pay duty. We both have nexus. We were directed to the long secondary screening line - it took about 45 minutes to get to the customs officer. No problems with the customer officer -that took no more than a few moments - he just calculated the duty and he directed us to the cashier.

In the past, we have come to Canada directly via YOW or via YVR and we have had to pay duty - the cashier is in the main hall, so we go there, pay the duty, and then are allowed to depart the customs hall with our luggage. (I have never had to pay duty when arriving in Canada at YUL - so I do not know what would happen there).

So it is advantageous, especially if one has nexus, and if one has to pay duty to the cashier, that one not come via YYZ - if waiting in line is a major issue.

PS-fortunately, I had not booked the first connecting flight from YYZ to YOW, or I would have missed that flight; unfortunately, with our flight from MXP arriving 30 min early, we could have connected on that earlier YYZ-YOW flight, with the help of the YYZ concierge - if not for our delay in standing in the secondary screening line for 45+ minutes.