in the good ol days, they both were "deliveries", sedan delivery, panel delivery - "commercial car" or truck - depended on your business and how much of what you "delivered" and where, the 3100 panel might not carry much more than the SD, but the 3800 sure will - grocers and flower shops for example would tend to use the SD for "town deliveries" where they wanted more agility and class - traveling salesmen commonly used them when the bussinessmans coupe wouldn't do - wholesalers and tradesmen tended toward the panels if they needed an enclosed delivery vehicle for "town and country" deliveries that weren't so bulky as to need a real freight truck, and farmers would find the panels more useful
I've had a number of sedan deliveries and always preferred them over any other car model, even station wagons, but panels fit my business activities better, and I've had more of them over a lifetime
geez, friday already?? my calender still says January

Bill