The term for the combined cone area and how far they move is called SD.
Also in consideration if how long the voice coil is compared to how far they can move and being under control properly.
Multiple small drivers can do what any big driver can do as well, if used correctly can even be used to cancel out issues many particular drivers tend to have.
I like the sound of big drivers but also the sound of small ones designed and used correctly, both can be very satisfying.
I have had horn systems that would blow away most all big driver systems in dynamics and incredible overall live sounding output and they used very small drivers.
I was also designing a very high end and complex system for a car project with massive horns built into the vehicle and dual 21" infinite baffle subs before I decided to go full time RVing so I sold that project off.
There is simply no one solution for what can be archeived for any particular size of drivers. Then of course first and foremost the space it will occupy and room treatments being top priority, always.
My next DIY speakers are going to be Frugel-horn Joan with Mark Audio MA200 eight inch full range drivers just because I have not done this before and it should work really well in our full time RV where my Egarhorns are the wrong design and far to big, line arrays I have might work, wanted to go with OB but not a good place for it....I could end up building something else but I like the idea of no crossovers and my little Baby Sophia 10w PP amp, fully upgraded of course.
Rick