So "regular" epoxy consists of resin and hardener, while JB Weld consists of resin, hardener, and powdered steel, I believe? That would explain how cured JB Weld is substantially harder than "regular" epoxy when cured, and can actually be drilled and tapped. The suspended steel particles give it the hardness that regular epoxy doesn't have.
JB Weld is not significantly "stickier" than regular epoxy as an adhesive, but harder when cured. Correct?