Now that's a really cool piece! What's the difference between the resin and the hydro stone plaster?

The primary difference in me end is cost. Polyurethane resin comes in at about $0.43/oz and hydro stone plaster costs between $ 1.00 and$1.50/ cured pound. Meaning it cost less to cast and is less expensive for the costumer. Drawback is that it is less rugged than the resin.