Small drivers vs big drivers

Even if size isn't everything, without certain minimal size there is nothing. One 8" woofer with good amp in an acoustically correct mid size room can accomplish a lot, but if you really need to go down clear full and loud - no. I like as few drivers as possible, but that's another subject.

I'm not sure the bending force on a small cone caused by the surrounded is actually a thing. Smallers cones are vastly stiffer than large ones and the resonance of the surround is so far out of the pass band of a woofer as to make no difference. What's more, several small drivers in a column behave as a line source simulating a woofer that is tall as the array in it's directionality. 

I think the bottom line boils down to the size of the space you need to fill and the listening distance. For small and medium sized rooms, several smaller drivers in a more narrow enclosure will yield better imaging just because narrow speakers do that better. If you can get further away from the speakers and reduce their angular size from your listening position, then larger drivers might be the ticket. 

I'd add that there are a few other considerations to factor in that I've observed...from a listening perspective:
1.  Are the listeners ears more sensitive to 30hz vs 80hz which will influence their overall perspective of the quality and quantity of bass depending on what the speaker is actually putting out.

2.  Is the listeners body sensitive to bass that is felt and does this influence their perception of the bass they hear
Why is this important....if you have a subwoofer, you know that when it is on and you turn it off...the soundstage collapses....therefore, the amount of bass, the quality of the bass and the physical force of the bass can greatly influence the soundstage.
None of these are very obvious from just the specs alone....and the room has a huge affect because on the nulls....if they are at a frequency range that is key to your own specific hearing/feeling of bass, then the soundstage will seem small...even though the louspeaker itself is doing a good job.

mzkmxcv said:

"the more it can move back and forth, the deeper it can go."  

With all due respect, I don't think this is accurate.  The more the cone can move back and forth is more a function of the volume it will play a given frequency,  not the frequency it produces.  The frequency is a function of how many times per second that movement is occurring.