The ket booby trap is a very slow detonating, single large explosion that leaves fire on the ground after it explodes. The PG booby trap explodes faster, multiple times and is slightly weaker and doesn't leave fire. Ketty booby traps aren't improved when you unlock the PG power. They're fairly useless since they take so long to detonate.
Partisans won't have booby traps next patch. They've undergone several changes.