[phatdaddy]

The cheaper is a polyester resin that uses MEK as an catalyst to harden. The MAS,WEST, Etc is a 2 part epoxy that need to be mixed in a ratio to harden. most production boats are built of polyester. if you use epoxy , gel coat will not stick to it and you must paint when done. epoxy is a little easier to work with because of the more predictible pot life. A lot of people use epoxy on components that will be hidden and poly on the exposed surfaces. epoxy will adhere to poly, but poly to epoxy is not a good bond. all of this is just my experience and subject to review.