Bass Driver Size - how much better is an extra inch?

Much value being offered herein albeit cryptic. 

Room fullness makes all the difference in the world, and with no distortion these simple things will rank a speaker very highly.  

High end brand names take notice.

B&w 802 speakers, $22k, have two base drivers at 8 inches.

to me that still seems restrained. 
Better to have 2 smaller base drivers vs 1 bigger size?

Makes sense very large drivers loss some ability to handle detail.  So there is a sweet spot between, say, 7 to 12 inches. And beyond 12, you would be in a subwoofer zone where detail is less important and less feasible.  
Personally, 10 inches on the b&w 800 seems ideal.  
There is only so much tech research can do while trying to cruelly shrink a bass driver and maintain sq.  Physics has its limits
Manufacturers and designers need to wake up and not artificially  suppress quality bass sound to accommodate a smaller cabinet.  How cheap are things getting.  Remember how they trimmed the size of a carton of oj a few yrs ago.