In regard to diesel there are a couple of debits. I carry disposable plastic gloves in case I encounter a filthy fill handle and I grouch at that inconvenience under my breath every time I fill up. The other is at a service station you might be relegated to a truck lane without a credit card payment at pump or you'll be limited to a couple of end pumps at the main auto bank. I did notice in Canada that diesel was much more universally integrated with the pump banks and two years ago was cheaper than regular in the western provinces.
In regard to tank capacities. I have been doing a little bit of research and noticed for 2014 that Advanced RV has increased the size of their tanks to 40 gallons fresh water, 26 gallons grey water and 18 black water. That's getting up to Class C size and surpassing in some cases. I understand that is a true 40 gallon tank as Advanced RV does not use a 6 gallon Suburban hot water heater but an on demand Espar diesel powered heating system heat exchanger. So you have hot water all the time because when on shore power the electric heating takes over.