My view from the UK - is that leather is considered 'better quality'. It is certainly more expensive - and I suspect if well looked after would last longer. I have a leather bag, bought new 40 years ago. It remains in excellent condition despite a lot of use ........ but so does its canvas shoulder strap!
It is easier to wipe mud from leather.
Personally, I'd buy leather, but most important is the quality, stitching, strap attachments (some the strap goes right round underneath to take the weight) whichever material you choose.