Finally, for players who blow through all of the strings listed above, Kevlar Hybrids are the final alternative. The superior abrasion resistance of Kevlar makes it the most durable string available. String Gauge Generally speaking, thinner strings offer improved playability while thicker strings offer enhanced durability. A 15L string is thinner than a 15 gauge but thicker than a 16 gauge string. Thinner strings also provide more spin potential by allowing the strings to embed into the ball more.
Truth be told, synthetic gut is nylon.
Nylon was so bad that only beginners used the stuff. It's that much better. Often overlooked due to it's cost, natural gut is the best choice for players with arm problems or those who simply want the best. Polyester strings also experience rapid initial tension loss. Players switching from a nylon or synthetic gut string should increase tension 3-5 pounds.