I like nylon leashes for running/traveling because of how light they are. But for day-to-day walks and for training in general, I prefer the heft of a leather leash and collars. It takes some time to break in, but the weight and feel of the leather helps give you and your pup a much stronger awareness of where each other are. I love our gear from Sexy Beast Dog Collars! (Best to just click on the link and not google that)