I use both the kill switch or key at times and never really thought about it...Same. Always thought a kill switch is intended to turn all power off, so the engine, in an emergency. Hence it's big and red.
No point having key ignition if the makers wanted the kill switch to be used as such.
Idk
I used to teach students to use the kill switch to shut off the bike because technically you don't have to take your hands off the bars....then once the bike is shut off, reach over and turn the switch....
I've been doing this for several (over 40) years with zero issues...