Grade 1 to Grade 3 Insulation

Was looking through some paperwork for my 2007 Inca, which is our first and only MH so far.
It has Grade 1 insulation, the current standard seems to be Grade 3.
I just wondered if serial AS owners who have moved from Grade 1 to Grade 3 over the years can say how much of a difference they notice.

I think the change is spec only has real impact on the water system with tank heaters, etc fitted.  The large amount of ventilation and large windscreen area are the main factors in internal temperature and they have not changed.

Peter