In my experience the picnic has more flavor then the butt, but the picnic doesn't yeild as much product as a butt. Fer large groups I buy both an mix.
Fer caterin, I place the meat in a roaster an rewarm that way, usin some saved juices fer keepin it moist. ALWAYS heat to over 140* an maintain that temp!
Keep the lid on, saves it from dryin out. Ya can use chafer pans to, just watch yer temps, don't wan't it gettin to hot which will dry it out an over cook it an ya gotta stay ABOVE 140*.
Apple juice will work as a moisturizer as well. Ya gotta watch how much finishin sauce ya add, cause it will continue to break down the meat, I add some durin pullin an then put a bottle out fer the folk ta add more ifin they choose to.
Long term storage, I put the meat in vac bags, then put on a big pot a water an bring ta a boil, turn it off an put the packs in it till they reach 140*. Nice an juicy!