But how much is a reliable switch worth when you're truckin' through a Class
B and all hell breaks lose?

In addition to the built-in PTT switch on the 172 I rent (with my Dave Clark
headset), the plane has a standard hand-held mike installed.

I also carry my own hand-held mike in the bottom of my headset bag, giving me 3
mikes.

Talk about 'belt and suspenders'.... :-)