Polyester (aka Dacron) looks and feel like nylon but has half the stretch and usually comes with a green tracer while nylon has a blue one or none at all. It also best against abrasion of all the standard fibers. It is heavier than nylon but doesn't absorb moisture like nylon. It is best where low stretch is desired like utility boom trucks as often low headroom is an issue and is less conductive than nylon in case it gets wet.

Dyneema or UHMWPE (ultra-high molecular weight polyethylene) is an amazing new fiber of incredible strength per strand and is stronger than wire rope of the same size. Its coating gives it very good abrasion resistance and 12-strand construction is non-rotating and easy to splice. We splice 4" eyes on both ends to allow it to be flipped to get double the life out of the same piece of line.