Really doesn't matter:
Acoustic feed back is the Mandolin top, with the Pickup sensing the vibrations
becoming a Microphone Diaphragm and hearing its own Monitor Speaker which is making the top vibrate and the pickup closes that feedback Loop.

either (any) will do .

You work on the speaker/monitor placement Stage sound level and the Room, to reduce that
(& Perhaps have a way to cut the feedback down, thru a Multi Band EQ)




Only A Solid Body with a magnetic pickup becomes really feedback Resistant..