Dyson's 13 oz polyester is extremely tough, but it's also a bear to sew if you're trying to stretch it around curves. It might not be too bad on a canoe, since the curves are gradual and you'll have to seam the ends. Any fabric in the 12 oz. + range should work for you.

Bill Lowe used to coat his kayaks skinned with 13 oz. poly' with 2-3 coats of Zar exterior satin oil-based polyurethane, followed by a single coat of Gaco UA-7000 2-part poly on the hull only. Those boats were incredibly tough. At Bill's insistence, I ran one over oyster shells and it didn't even leave a mark.

That said, any 2-part finish will be more durable than using only a 1-part finish. If you don't like the price of the 2-part stuff (it's very expensive), the next best thing is probably Dura-Tuff varnish, but it comes in gloss only. It's more expensive than other 1-part finishes, but cheaper than 2-part finishes. Personally, I just use the Zar and it holds up well. It's relatively inexpensive and it's easy to re-coat when necessary.