I use Nylon most of the time. I don't like our flexi leash. I find it really flimsy and don't trust it at all. It's nice when we're walking on a long trail though(Kai doesn't pull because there's nothing to scare him) but since we live in a busy area, I just use the nylon.

I'd like to try a hemp leash though. I heard they get stronger as they get more worn in.