Vinyl Ester is chemically a lot closer in the Linking and structure of the polymer chains to Epoxy than straight Polyester. This is why it is more tolerant to many chemicals.

Vinyl Esters, Generally have a lower shrinkage rate and therefore less internal stress within the laminate. Because of this, the laminates are similarly strong to Epoxy laminates. Working with Vinyl Esters is very similar to working with Polyesters. The catalysts are mildly different but the cross linking and curing process is similar.

There's 2 ways to test whether you have Epoxy or Polyester. either way you need a small piece of the laminate that you are prepared to destroy.

1 - Get a solvent (MEK - Methyl Ethyl Ketone works well but Acetone will also work - it just takes longer). Apply it to the laminate and see what happens. If it is polyester, the surface will become "Tacky" fairly quickly, If it's Epoxy, it wont (at least not for a long time).

2 - Burn a piece of the laminate - the smell will give it away.