For me, I dry camp almost exclusively. It is important for me to include a full tank of fresh water in my calculations.
I've been looking at small lightweight trailers that meet my layout needs and can be towed by my Durango. I have found that in lightweight trailers, the CCC can be severely limited with a full fresh water tank.
So, it really depends on what you plan on doing with the RV that determines which data is important or not.
As an example, I saw one trailer I liked. It's dry weight was about 2500lbs. It's gvwr was about 3100lbs. But if I filled the fresh water tank, it left me with only about 360 lbs. I felt that was way too close to the edge to feel comfortable.