@Etexhorn13 hit the first major difference with what is likely a substantial increase in overhead. Margins shrink with increased overhead making even more important to sell everything. What happens if you smoke a brisket for Thursday and it doesn't sell? Sell it as sliced brisket on Friday, repurpose it into chopped beef or chili, or vacuum seal it and sell it whole for takeout. Small places, like the one in Mart (pop. 2500) are in a real bind because they likely don't have the ability to move many whole briskets. Chili and chopped beef can't be sold for high price per pound as sliced brisket (the place in Mart didn't have either on the menu). There are serious quality issues with briskets held for multiple days.
Dozier's made the mistake a few years ago of selling older brisket to Daniel Vaughan and were called out on it. To his credit, ChampKind admitted that they didn't cook on the day off and sold older brisket. He also committed to start cooking on the day off. Vaughan returned a couple days later and the food was much better. TM Article
I don't know how much better it is to sell from a food truck, but I suspect it is better to build a customer base from a food truck first and then weigh opening a brick and mortar. Victorian's Barbecue established a reputation in Houston in a food truck and then moved to the middle of BFE and opened a brick and mortar. I wish them luck, but it's going to be tough.
On the way back from Mart on Saturday, we stopped at the Temple location of Pustka Family Barbecue. They ran a food truck in Hutto for several years. A couple years ago, they move to their new brick and mortar location in Temple. When we pulled up at 2:00 there was no one in the parking lot. Sign on the door of the building said indoor dining and order at the trailer. Talked the the owner and his dad for a few minutes. Because of City permits and such, they are unable to operate out of the building and everything is still being prepared and served from the trailer. They made the mistake of trying to start a restaurant in a building that was not previously a restaurant. They do a great smoked chicken, but unfortunately they didn't have any. I ordered a half pound of moist brisket and a couple ribs to take home. Even reheated the food was pretty good. The ribs were seasoned well and cooked perfectly.
If I were inclined to start a barbecue business, catering seems like the best bet for success. While waiting in line at Interstellar Barbecue, I chatted with the couple that owns Clutch BBQ in Houston. They do catering and the occasional pop-up and seem fairly successful at it. They discussed the possibility of opening a restaurant and I told them they were crazy.