Both very durable on a properly prepped surface. Combined with #601 PBA hard to beat for longevity. On their own I would say that the 105 has a slight edge. Both very close in terms of longevity but in the past two years of using both I've noticed that the #105 will maintain tighter beading (smaller) over a longer period of time. The #501 lasts almost as long but the beading gets larger sooner.