Carry it on.
One pass through the checked luggage x-ray is way more exposure than several passes through carry on. Also if you're carrying it and ask for hand inspections, you'll be successful a few times and the fewer passes the better. Not to mention if it's with you know it's not going to get really hot and cold, wet, squashed or whatever. You'll have to shield it well, physically protect it well and still hope it's not run over by a tug. What the worse that can happen? They make you gate check it anyway I suppose.
If you remove the film from their cans you will have a better time getting hand inspections, they don't like things that are sealed since they have to open each of them.
My only experience internationally was Luftansa/United (code share) Denver to Frankfurt, non-stop in 2006. So we only had a couple of security check points to deal with. They honored my request at all but one of them, so my film only had one pass through carry on. I had 100 and 400 Fuji E6, no apparent issues. I carried it in a plastic bag with a zipper and no cans. Made it very clear, quick and easy to see. They only had doubts with the exposed rolls since I roll the leaders in on finished rolls. With unused rolls the leaders I think made them less nervous. With used rolls coming back home they swabbed them and ran some sort of test, I assume checking for chemical markers that indicated something either good or bad. My German was not good enough to understand esoteric chemistry and they weren't exactly chatty about what they were looking for.
I've also heard of people using shielded film bags, letting it run through the carry on and dealing with the inevitable hand inspection. Sorta forcing them to do a hand inspection without asking. I think this might piss them off, but it guarantees your film has minimal exposure. But films now a days are better about x-rays exposure and so unless you're using high speed 1600 or 3200 film, a pass or two isn't gonna kill it like 20 years ago. Also the inspection machines are better about blasting everything like it's a microwave. They are more sensitive and need less power to get detail.