You are looking at your decision like one is better than the other. You must look at it as two different products that do two different things. In the end, the best one is both, as you may need both to do what you want to do. Your gym/work may not use HF tags, so the xNT won’t work. Maybe they do use HF tags but its an encrypted tag, again it won’t work. So while I agree, the xNT is capable of possibly more of things that you want to do, it most likely won’t do everything.
Take a peak here to see the different types of tags that are used…