Super Sap: I started using Super Sap a few years back because I was looking for a "green-er" epoxy for the company. It's a good, high performance epoxy, like most name brands. When you get down to it the bio-based benefits mostly come in to scale for large volume users. It IS good for marketing.

System Three: I was given some Silvertip for use on a project a few years back. A customer bought it in a kit and couldn't finish the project by himself. So he had me complete the project. It was a nice epoxy. I just didn't find it particularly any more remarkable than other brands (MAS for instance).

Honestly, I'd buy more of what you're use to using. For the boats that are built here there's not much difference between the brands, save the low-end, cheap ones. You do get what you pay for.