Side dishes are your friend!!! Who is supplying the side dishes? Do you trust the person supplying the side dishes enough to guarantee your reputation on what they supply. We are BBQ people and meat is our "Forte," so we like to just cook meat.
This is my experience--early in my catering career I did a few jobs that were "Meat Only." I cooked plenty of meat for a wedding and the person supplying the side dishes ran out of all sides before half of the people were served. Our BBQ pit was sitting there proudly lettered with our signage. My wife was at work the next Monday and one of the workers was talking about the no good folks at Chuck Wagon BBQ Co that ran out of food. The meat never ran out. I could tell you several more stories.
There is no formula for figuring beef VS chicken eaters in a food line. If serving is in a buffet line then people will see both meats and human nature will cause them to want both meats. If they are served at the buffet line and are asked "Beef or Chicken?" most will comply--but someone will ask for both. If that one person gets both then everone else will see it and will be angry at the caterer. When I serve buffet style I make sure there is enough of each meat for each person to take both. If we plate the food and deliver to tables at a formal gathering then beef or chicken will work.
Most caterers will say--"I can't do that--my food cost will go up" If it is done right food costs will not go up. Most people do not want 1/2 chicken, if there is 2 meats they won't even want 1/4 chicken. A two meat meal with chicken as one of the meats calls for 1/8 chicken per person. We cook the chickens as halves then split into quarters then cut legs and thighs apart and split the breast and wing into 2 pieces. It is easy to figure out--just buy one chicken for every 8 people. 175 people would require 22 chickens. If a whole chicken costs 5 dollars then the cost per person between 63 and 64 cents per person.
Put the dishes on the buffet table in order by "Lowest Cost First" Usually bread first then salad then beans or potatoes, etc. Make plenty of side dishes and have plenty on the table. Then come the meats--chicken first then brisket. Make sure that the chicken tray is overflowing and the brisket is half empty, and refill it constantly. Human nature will take over--plates will be so full of side dishes that there is little room for meat. The trays look like there is alot of chicken but the brisket is lower--so people all take chicken and go a little easier on the brisket.
Awesome quanities of side dishes will save you money--the more people that eat chicken save you money on the more expensive brisket.
We always serve buffet lines this way and do not even have servers dishing out the meat. We have never run out of food and we always have seconds. People feel great about the meal and leave happy and we get referrals from every job we do. The money that we save hiring servers to serve the meat can buy a little extra meat.
Brisket has a lot of weight loss due to shrinkage and fat trim. I would get .75 pound per person raw brisket or approx 130 pounds.
130 pounds brisket will cost about 260 dollars
The chicken will cost about 110 dollars
total meat cost $370 or $2.12 per person -meat cost only.
I could go on and on about "human nature" in the serving line---and what works and what doesn't work and why it works or doesn't. I am not being a smart azz---I just have learned many things the hard way.