There are three types of load switches:
1) A simple on/off switch on the load output
2) A soft power switch which controls a relay on the utput
3) A soft power switch which electronically controls the output to ensure that it ramps at a certain rate or whatever. Often it won't even disconnect the output, it just ramps down to zero volts.
#1 and #2 are essentially identical.
I'm not a big fan of #3, and I prefer #1, because often when testing gear I'll want to simulate real-world plugging in of the power to the device under test, i.e. contact bounce etc. With a real power switch I can "fiddle" with the switch and make it do some horrible things to my DUT
Dave.