dion isothalic resin/ flat weave glass

I read somewhere about dion isothalic resin; does anybody know the advantages and disadvantages of it? Is it similiar to polyester or more viscous like epoxy? Also, is it much more expensive. Also, they said flat weave glass (6 oz. volan) held less resin than normal weave, what other weights and types of glass are flat weave? Is it much better really? Thanks for the help, ryan