Do i really need a TT with enclosed underbelly?

I also have owned both and don't see any difference in floor temps but our heat is ducted through the floor. The big difference in floor temps comes from skirting the RV.

I actually prefer not enclosed because of the ability to see leaks or problems arising. My water tank is enclosed with some form of cardboard and braced outside the cardboard but the holding tanks are not, there open.