Just to be fair, I've never used Granitex. However, I am somewhat familiar with Vortex. Pride Custom Coatings (owns Vortex and Granitex) certainly is not recognized as a leader in the coating industry. But, that doesn't mean Granitex is a bad product.
Granitex is a combo resin of aliphatic polyurethane and polyurea along with isocyanate as the hardener. It's closer to a polyaspartic polyurea than anything else. I would recommend you request the Granitex technical data sheet (will show tear strength, tensile strength, elongation, etc.) and compare it to another brand of polyaspartic polyurea.