There are so many variables in this business it is almost impossible to make a rational decision. I'm trying to research this as a possibility in the future.
As you mentioned above, you are confusing yourself. You are doing this by blending categories and assuming that one answer applies across the board. Spec'ing a truck is a process of making trade-offs. It gets easier when you realize that the categories change depending on what you are looking at when you consider them.
Examples:
You are thinking about a C-unit. "C-unit" changes depending on the carrier you are considering. So before you lock yourself into the notion of a C-unit, you need to lock onto a carrier. Then you'll know if B or C applies.
But the real thing you are thinking about is a truck that does not trigger the hours of service rules (log books). So you abandon the B, C and D designations as a primary consideration and let those chips fall where they may.
But why are you making no-log-books a primary consideration? You gave the reason. It is because you are ASSUMING that you can haul more loads if you do not have to log. But have you really thought that through? Physical limits still apply. You cannot drive safe when tired. Is there so much van freight to be found out there that someone who does not log could run 24/7 if not for the physical limitation? I don't think so.
Maybe you can make more money by logging and hauling more weight in a straight truck.
Is it the money that is driving your assumption about not logging? Or is it the fact that you don't have, don't want, or can't get a Class B CDL?
Straight trucks cost more than vans .... but wait, that may not be true either. You may very well be able to find a good used straight cheaper than you can find a new van; at least when you think beyond price and consider future useful life.
It can get confusing very quickly if you don't get specific about your categories, and even more quickly if you start thinking about the kind of truck you want before you identify your other priorities and expose your assumptions.
To clear things up, don't begin by thinking about trucks or CDL types or log books. Begin by thinking about yourself. Ask, "What kind of expediter do I want to be, and why do I want to be that?" Or, to put it another way, ask, "Why do I want to be an expediter, what am I trying to accomplish really?"
Once you know the answers to those questions, it will become easier to sort through the rest.
Notice that there are many business models to choose from. There are some expediters who define success in terms of what they don't want. They go out on the road because they don't want to be home with the wife. They drive a van because they don't want to log. They structure their business to break even or lose money because they don't want to pay taxes.
There are other expediters for whom the primary consideration is keeping busy. They don't want to sit. They want to roll. And they'll do so at almost any price, as long as they stay busy. Profitability is a secondary concern.
Some people want to be expediters because they hate their present job or (un)employment situation, and they feel better when they dwell on the expedite dream. They know nothing about the business except that it feels good to think about it, and for that reason alone, they want to be expediters.
There are others that have an annual gross revenue goal in mind. Still others have a net-worth-at-retirement goal in mind. And there are many more.
It's not about what other people are doing. It's about what you want. Get clear about that and the rest will fall into place.