Canvas Bag?

I have just started to enjoy sparring, got black eye right now, another story though. I was wondering if anybody could tell me the difference between canvas and pvc pucnhing bags.
Cheers

 

pvc is cheaper

 

pvc hurts more when the pads/bags get old and start to crack.

 

I used to have a canvas heavy bag, it actually started to go mouldy! I replaced it with a PVC one after all my training stuff got stolen a few years back.

I find the canvas is more likely to take skin off my knuckles if I go at it for a long time too.