Vinylester is sort of epoxy. It has styrene in it, it uses cobalt and peroxide, but also has bisphenol-A epoxy in it. So it has good compatibility, better elongation than polyester, and no amine hardener which causes allergy problems. It isn't the BEST of both worlds, but in my opinion is a nice trade off.
http://www.mertons.com/Epoxy/polyest...inylester.html
Edit: dropped the napthenate- some use cobalt octoate