OK, I think you have your terms mixed up.
A "Dead Man Switch" is the one where you must keep your foot pressing on it to keep the saw running. (As long as you are alive, the saw will run, if you die and your foot falls off of the switch the saw dies with you.)
The other one is simply an "On/ Off" switch that is activated with your foot instead of your fingers.
I prefer a dead man switch for ease of use and some control over speed and quickness of stopping the saw. Other people have their preferences of course but, I can just see myself stomping all over the floor with my foot trying to find the pedal to stop the saw.
The idea of a dead mans switch was a safety devise for big machinery that required a person to be in constant control and not have a "run away" with nobody controlling the machine. (Think train engines for example.)
Rog