hands down, kings are the best!
since your other thread was looking for a short launcher with trigger, I can assume you're not getting the xm203 short which won't fit the kings.
but, I have never tried to chamber a king into a short launcher with a trigger.
for maximum range, kings or cherries.
for wider blast area but slightly shorter range, *snicker*, use the multipurpose nades.
for shortest load time, use the multipurpose nades but make sure to pack some tissue to act as wadding.
for maximum giggle factor, kings all the way at 900psi!
I have never used the slugs, but as you mentioned, finding them will be a pain.