Thanks for your questions. The Bass Array12-3 is the size of many other premium 12"/tweeter cabs. So if using a single cab like these on the floor its best to be forward of the cabinet a few feet. The BA12-3 provides a much broader horizontal dispersion when compared to conventional 12"/tweeter designs which testing and live performance use bare out. There are several comments on TB from users regarding their experiences that support this.
In both the horizontal and vertical planes the experiences have been a more controlled dispersion through out the entire bandwidth being reproduced. This also results in a much smoother response due to the small cone drivers reproducing the critical upper mids and highs as well as how balanced they are at the crossover point with the 12" woofer. I'm not going to say that the vertical dispersion is "better" than a 12"/tweeter cab but it is more controlled with the BA design. As well the BA12-3 offers an extremely flat response across it's bandwidth. A conventional design is more likely to have a mid dip as the freq rises and then the tweeter rolls in. Another consideration is that as the frequency rises in a larger format woofer, the dispersion tends to narrow, which can result in some level of beaming.
"Live" reports have been that even when using a single BA cab the band hears the bass much better on stage, as well as in the venue. If you search around the forum or other reviews of the BA cabs, I think you'll hear similar comments from users in the field.