As one who has changed tire load ranges on various vehicles over the years, and kept the inflation at the vehicle manufacturer's recommendations, I can state from experience that there is a HUGE difference between a Load Range D tire at 65 PSI and a one size larger Load Range E tire at 65 PSI!
There is less tire squirm, less wander, a firmer ride, and IMO, a better driving experience.
I also use M&S tires on all applications. Traction is a wonderful thing!
When I put new rear tires on the Southwind, Load Range F were not available, so they put Load Range G on it. I had them inflate the G tires to the same as recommended for the F. The difference in handling was incredible! When I have to replace the front tires, they will also get G rated, and be inflated to the coach builder's specs.
Anyway, regardless of what the "experts" say, I have found that increasing the load range DOES have benefits, even when inflated to the same pressure as the l0ower rated tire.
Just stating personal experience. As always, YMMV.