chopper gun or hand laid means nothing. type of resin is all that counts. there are many different tiers of resins. just like paint there is good better and best with 50 qualities in each. epoxy is the upper tier, vinylester then polyesters. i use epoxy resin for any repairs , vinylester for any mold work , polyester for things like speaker boxes and such. the key to resin work is cure. best way is to wrap in black plastic and set in the sun for a while. exposed to higher temps than normal.