the poly rope is just fine and in my opinion a better option since you always need rope, this way it can have a dual purpose. straps, not so much. google/learn the trucker's hitch knot and you will be able to secure your canoe atop your vehicle as tight as you want quickly and easily. a good test to see if it's tight enough; if you move the vehicle when you try to move the canoe atop the roof it's good and not going anywhere. i've car topped canoes many many times across long distances. tie the rope to the two bumper support each front and rear of the car and for extra security, run a ratcheting strap across the middle of the canoe, through the vehicle (rear doors if 4 door). to eliminate the strap from humming at speed, twist it.