I have used both and noticed little difference in yield.
Ours have very little bone in either end, but I think on reflection, I agree with you about the picnic--not quite as good,BUT if on sale, I'll take it!! LOL
Have gotten 14# double package at Costco, cooked it and gotten enough for 40 people often.
I would never cook BBQ covered--people LOVE that crusty part mixed in with the BBQ--I chop that with a cleaver--and actually for large amounts I chop it all--pulling is just too hard on my wrists for a huge amount.
Having leftovers of BBQ isn't a problem so if you did cook 1/2#/person, you will have some I think, even feeding teens. Even at $1.50/lb. (what it is here now), BBQ is a bargain per person finished.
You might look up Lexington slaw for a different slaw to offer (along with the mayo based). It is tangy and delicious. It has a finer texture chop to the cabbage--almost ground. I can get it by shredding the cabbage and then giving it a whiz with the metal blade in the FP.
And as you know, your yield of sandwiches will be MUCH more if someone is serving/spooning out the BBQ, rather than what folks will put on their plates. When catered, the servers do the serving. Just a thought. And many, including me, serve themselves an open face BBQ "sandwich" rather than a pickup kind, so a larger basic serving.