What does it change between polyester and nylon Slackline?
Most of the longline webbing are made of polyester: this because it is easier to tension. On the other hand, the nylon lines are much more elastic: at the same tension, nylon stretches up to 50% more than the polyester!
For a better use of a nylon Longline, use them over a land with depressions (basins); the nylon webbing has a greater bounce than polyester. They are good, to practice highlining and waterlining: limit the stress on the anchors and reduce the risk of cuts and abrasions.