I personally prefer to ground tie, and my guy does it-WELL.
3rd choice-nylon breakaway.
4th choice-Rope (but since I usemy rope halter to keep him in lone a lot, this ends up being what I use most)
5th choice-all nylon. HATE them. IMO they are fine for hand leading, or riding in a halter (but I prefer my rope one there too). They just will never break, and with the lack of pressure points, IMO, they are less likely to help you get the horse under control IF there is an issue. They give minimal control, compared to rope, and, frankly, other than the fact that they are like $5 a piece, and come is all sorts of cute colors for the teens, I am not a fan.