hoosiemark,
That's not a Class B, it's a Camper Van.
You are doing the right thing by sitting in the different RV's, and trying to imagine how it will work for you.
Test drive them, a Class B drives much different than an RV built on a truck chassis. Most Class B's will be quieter, with less rattles, because they are converted on a one piece van chassis.
Spend as much time without the salesman, you will eventually choose the one right for you.
You can't have it all, it's all about making the correct compromises. For a lot of people gas mileage is one of the major deciding factors.
Good luck