As you can see it's personal preference.....but that comes from having some experience which you don't have. Mine is enclosed and heated, no tank heaters though and the heat going to the underbelly consists of a 2 inch takeoff from the furnace stubbed off about 2 feet into the underbelly...that's it. It's kind of like the lightbulb in the wellhouse, it's enough heat to keep the important things from freezing up usually.
While you may not think you will ever do any cold weather camping there is always the possibility of running into cold weather. On one trip home from Florida in January we stopped in Georgia for our halfway overnight...it hit 23 degrees that night. Better to have it and not need it than not have it and need it. I had dumped the black and gray tanks before we left FL thank goodness and used the CG facilities but kept the fresh water until we arrived home.