There are several advantages to minimonitors:
1) The drivers are so small and close together that they come pretty close to forming a point source.
2) The front baffle is very small, eliminating most diffraction distortion--the time smear you get from reflected sound waves bouncing off the front baffle.
3) With such small box panels, it is easier to build a minimonitor free of enclosure resonances.
4) A 2-way speaker with a small mid/woofer has less time lag in the separate arrival times of the woofer and tweeter elements. Minimonitors are inherently *almost* time-aligned. Their ability to "disappear" while throwing a large, well-delineated soundstage is captivating. Their speed and clarity make small-group acoustic music come alive--think small jazz ensembles and acoustic folk/pop (James Taylor, Sarah McClachlan, Joni Mitchell, etc.)
The disadvantages are, of course, small radiating area, making it a struggle to scale up to large complex pieces and fill large spaces, bass extension, and dynamics at both ends of the spectrum.
That's why there are premium minimonitors that use mid/woofers capable of greater cone excursions to be able to play louder and go deeper while retaining the decided advantages of a near point source mounted in a nearly inert cabinet with minimal front baffle area. Examples include the better Totem stand-mounted speakers (The One and Mani-2) and the Sonus Faber Guarneri Memento.
Still, I wouldn't likely choose minimonitors for a such a large listening area, unless it included powered subs that were time-aligned with the monitors--maybe a pair of Totem The Ones or Mani-2's plus a pair of JLs or RELs.