Two medium size woofers Vs One big size woofer

two 5" woofers is equivalent one 7" woofer , not 10"
this is simple , check any speaker design book

approximately

I have two Vandersteen 2wq subwoofers. Each has three 8 inch drivers driven by a 300 watt internal amp. They have a "Q" control on the cabinet back to increase or decrease the tautness of the sub response. The three 8" drivers with the "Q" set low provide amazingly tight bass. If you want it to boom, for home theater movie reproduction you just turn that dial up.
I just bought a new disc player and power cord for my system amplifier. The disc player is rendering a tighter bass profile and the power cord (7 gauge) has really given heft and gestalt to the bass and system sound overall.
On the other hand, one large driver can do a nice job especially if it is used in a servo controlled system.

How many subwoofers have you seen using ten 6" drivers?

I wonder how the larger surface area of a large woofer factors into the acceleration factor.  A large driver with twice the surface area of a smaller one only needs half the movement of the smaller one to move the same amount of air.  That has to factor into the equation.  I think you'd need to understand the relationships between size, extension, distortion, etc. to be able to have a meaningful opinion on this.  Big drivers are definitely better for deep bass.   You'd need 9 6" drivers to be the equivalent of my 18" sub and in order to have a comparable excursion the surround would need to have as much surface area as the cone.  That would have to contribute to distortion.