I guess I will join in the catering chatter, having served hundreds of thousands in banquets over the years. I may add some babble sense.
You guys are all real close, would you agree it is a matter of individual portioning skills. If your eye balling it with a spoon everyone is gonna yield different.
Mac N Cheese, Mashed Potatoes and say Diced Roasted Veges take up some decent plate coverage.
If I was using a halfhotel 2" deep metal pan filled to the top. I would safely count it as 15-17 Portions depending on group and are you plating of buffet?
I can't speak for the Foil Pans Medium Deep, never served a banquet out of those.
Tip I used to plan by: If I had 100 people and it was a corporate Party with say a industrial company or something. I would plan on 1.5LBS of food to be consumed per person in a two hr period.
We would calculate and consider everything for or final production by weight, then by group proifile, history, serving time and most liked on the menu.
Veges were always one less pan than potatoes.
-The goal I wanted maybe 1/3 pan or less of leftovers at the end of the night without running out.
"Garnish, We don't need no stinkin Garnish"