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

Have older b&w speakers and bass drivers are 7 inches vs 804 d3 speakers that are 6 1/2.

the larger drivers seem to really open the sound stage, more open and less constrained.  Imaging of older speakers not as good but a very enjoyable listen.
Not sure why driver sizes tend to be smaller these days unless you pay a lot more.  Hear that most consumers want more compact mains so drivers are smaller.  Kinda sad.