Why Poly ? Polypropylene greens are best for holding shots from a distance. The poly allow more space for infill material. Infill material of poly synthetic turf is what takes the kinetic energy off the ball when hit. Increase the infill material on the putting green, the longer the shot the synthetic turf will accept. Polypropylene greens have less contraction problems. Poly synthetic turf will not expand and contract and you can install in a large area..
Why Nylon? Nylon greens is one of the toughest fiber in the world. In terms of durability, nylon synthetic turf wins. Nylon greens also have far less maintenance due to the decreased amount of infill. Nylon synthetic turf overall has less mold or mildew problems. Again, this is due to the small amount of infill in the nylon turf.