The stock items are 7/16 polyester for the main sheet and 3/8 polyester for the jib sheet. I replaced my jib sheet with 1/4 Yale Light (spectra core/polypropylene cover), with which I have been very happy. My first Yale Light jib sheet lasted about 6 years before the polypro cover was shot (spectra was still okay). I am now on my second sheet for about 2 years. Last year I replaced my main sheet with 3/8 Yale Light after the original polyester sheet was shot (approx. 10 years). The cover at the blocks/cleat is already showing some wear.

Bottom line: The Yale Light is definitly "sexier". I do like the fact that it doesn't absorb water and I can use a smaller diameter but it does seem to wear faster and the "performance" difference is negligable. You may want to use your existing sheets for a couple of years before dropping $ on new sheets.