Silk + WBPU has a few advantages over glass and resin. First is cost, epoxy and glass costs more to do compared to silk and WBPU. Most people find WBPU easier to work with (with silk or glass). Getting a lightweight coating with resin and glass takes some know-how and many people get a lighter lay up with WBPU. Silk (and paper) both shrink while drying with WBPU. This imparts extra stiffness to the foam. It's possible to use this characteristic with a lighter structure to get lighter final weight.
If you like resin and glass, you should continue to use it. I've tried many methods to cover foam. Each has advantages but the one you have the most experience with tends to get the best results. Glass and resin has a reputation for being heavier but it's not if you know what you are doing.