Replace Wall Receptacle / Outlet - What's the Right Leviton Model
The standard and heavy duty are both 15 amp.  The standard outlet has back wire contact holes for 14 ga.  It is a leaf spring friction edge contact that will fatigue and can work loose over time.  The heavy duty 15 amp outlet is specifically marked back-wire.  The wire insert holes are larger to accept 12 ga.  The contact is a heavier jaw clamp forced down by a screw.

If the standard screw contacts are used, both standard and heavy duty are equivalent.  The heavy duty version just allows 12 ga back-wire installation that is reliable with screw clamp contacts.