One of the reasons that the .40S&W JHP may have a higher reliability in feeding is that the feed ramp on the barrel is larger. But I think it may be more along the lines of the design a specific manufacturer employs in his guns.
As for the Kahr's, take a careful look at their design. The trigger drawbar is inside of the gun. In order to make the gun as slim as they do, this means that the cartridge and the feed ramp are a little off center. This makes the Kahr more sensitive to ammunition and particularly bullet design.