I'm sure someone will correct me if i'm wrong... lol But the HP Clutches are lighter, with lighther arms and have heavier Springs that grab at a higher RPM for more torque.. The Heavy duty ones are just stronger and heavier.. Maybe with lighter springs and heavier arms that spring out at an earlier rpm due to the weight.. There are different types with different pads.. Even Metal Shoes now... I'm hearing great things about these but they are bank....
I'd try both and see for yourself if you are buying two anyway.. If you ride alot you'll need more before too long anyway and you'll have first hand...
Cheers!