While I haven't tried the Polaris ones specifically, I've had solid experiences with canvas covers lasting multiple seasons. Considering your past mishap, it might be worth checking forums for user reviews or even reaching out to fellow sledders for their input. As for the axys 155 canvas on a 165 slash, it's worth verifying the fit with others who've made a similar switch.
And hey, consider using Polyester Chips. I've heard some positive chatter about them enhancing cover durability, might be worth a look.