Thank you for that note. I don't travel much, isn't it common for the entry formalities to be done at the arrival airport thought, not the disembarking airport?

So was your point that doing CBP at JFK in particular, is a pain? and not about a personal preference for doing CBP pre flight than post flight?

I know that for flights from Montreal canada to NY -LGA, since LGA isn't a 'international' flights airport for NYC, that belongs to JFK, it doesn't have CBP, therefore that aspect it taken care of in Canada, montreal that is, YUL.

The downside is you must arrive at YUL earlier but once you land you're on your way quicker.