The object for most sailmakers is to come up with the best design, for a given boat, and use materials that will maintain this design over a wide wind range. There are two lifes for a sail,the life of the sail cloth, and the performance life. The performance life, is the length of time that a sail will matain its designed shape. The cloth life, is the time a given materal will last after being subjected to wind loads, flutter, UV exposure, etc.
In most cases, materals that have low stretch,light weight, and good durability are most prefered. There are always comprimises. The materials that best fit this discription, are also the most expensive.Sails made with low stretch materals, can be designed fuller. This gives more power in light winds, and will not stretch and become too full as the wind builds, compared to their more stretchy counterparts.Pentex is a good all around fiber for most beach cat sails. This fiber has twice the modulas as polyester, giving it twice the strength, and about 30% less stretch, as polyester. The price is also good. Using stronger cloth with less stretch, enables the sailmaker to go down in weight, as well. Jibs are often made with a preminum dacron called square dacron. This is a balenced weave and can be used in a triradial cut. This is a fairly low stretch dacron, and will stand up better to the abuse that jibs experance. The mains have many full battens that reduce flutter, they wear much better because of this. Laminates will last much longer in the full batten mains.
Dave