I have installed them on every rig I have owned for the last.... 30+ years.
I install them on other people's rigs too.
It really depends on your personal preference and the amount of time you want to spend installing it.
All you have to do, is make it very convenient and easy for you to operate, and "not obvious" to the car thief.
Basically you "break" the truck. So even with the keys it wont start. As long as the thief doesn't find the kill switch, then they would need to use a tow truck to steal the rig.
Disguise it as an OEM fog light switch, or a switch under the seat. You can put them under the sun visor mirror cover, or in the glove box. Next to the seat, under the dash, or it can be done with a remote control using a relay. You can tap into the fuel pump, ECU, starter, etc.
The most famous bank robbery in Hollywood was foiled by a hidden fuel pump kill switch on some old crappy pickup truck. One of the robbers tried to car-jack a truck during the escape. The driver said no problem, take it - and he flipped the fuel pump kill switch off on his way out of the rig.
That robber got caught.
After suffering a leg injury from police gunshots, the other guy blew his own brains out with a 9mm before capture.