I gotta chime in here with my experiences....especially recent ones.
Practicing in the ZZ Top band, we use the floor monitors for our PA. That works great. The drummer has his own monitor too.
1x12 cabs can be very 'beamy' - I mean, they can project in a straight line sometimes, without fanning out as much as an array of speakers. I too use 1x12 cabs and typically only hear one of them. Standing on the dance floor, much farther away, they sound wonderful and are in stereo, but you have to be in the center. A little to one side, you only hear that speaker.
Even with my speakers stacked and 'cocked' (the top speaker is rotated 45 degrees clockwise) to fan them out, the sound projects in two pronounced beams. They do cut through the mix really well, and they work great for using a mic on your cabs, but I have found them to be beamy, for lack of a better word.