My local independent pipe shop owner says the bristle pipe cleaners have bristles that are softer than the pipe stem material, hence no problem. I agree a crimped wire might scratch the airway, although I seldom see those. I have used tapered pipe cleaners but prefer the regular ones for most uses; I think it may depend on your pipes and your way of cleaning. If you have some fairly slender pipe stems and shanks, the tapered pipe cleaners can just be too fat. I feel like I get coverage with regular pc's by moving them around, and if they get bent a little bit, that also increases coverage. Churchwarden pipe cleaners are necessary if you smoke wardens.