Leather lasts longer, but it's not very flexible, and it sort of sticks to and squeaks on the floor.
Canvas may not last as long, but it's cheaper. It's a lot more flexible and comfortable, and it shows off your arch.
I've used both kinds and I definitely prefer canvas!!!
I think its personal preferance. I have both canvas and leather and prefer leather. At my class we have to wear leather so there isnt much room for thought. After dancing in leather i must say i find it easier to do so rather than canvas.
Leather is not as good as canvas becasue it does not show your arch off and they are harder to turn in.
Canvas is a great shoe if you have a high arc like me it well really show it off and they are much easier to turn in.