It looks like Cap-a-tread is a laminate product made to match laminate flooring. Unless you're doing the floor also, I'm not sure how that's going to look against your original floor.
NuStair looks like it would be a better match for the floor. You could use a circular saw to cut most of the bullnose off the old stairs and finish off the ends with a chisel. I'm not sure how things would work on the top stair. The NuStair tread at the top would sit above the finished floor. If you decide to not put a tread at the top, you'll have a step that's shorter than the rest. Come to think of it, you'll have a step at the bottom that's higher than the rest. Ask, I don't like stairs with attached nosings, I think they will come loose in time.
Are you sure you don't want to have a go at replacing the treads? I'm wondering if the treads sit on top of the stringers, or are inset into the stringers. If they're on top and not captured on the sides, it seems like it would be easier to remove the old treads and get new treads that already have a nosing than it will be to cap the existing ones.
Just a couple of other thoughts. You could fill the holes and paint them. Also, Flooring guys have all sorts of tricks to deal with messed up treads and ways to replace them.
Last edited by Quickstep; 05-02-2016 at 06:44 AM.