If I understand the concept correctly (remembering I'm guessing how the solid state system works) the main benefit is that the main load does not pass through the switch at all.

Normal switches are common point of failure, and because they carry ALL the electrical load their failure means no power. With this system the switch can fail, which will limit the ability to turn the power on/off. So, a failure of the switch during flight shouldn't interupt power at all.

Also, no vibration induced failures with the main load circuit.