I wouldn't compare one single BA10-2 to a big (studio) monitor/speaker, of course at the end it is still a single 10" driver no matter what... for that I would definitely go with the BA12-3.Compared to a smaller, near-field, monitor, I could see that being the case. However, compared to bigger monitors, listened to at an appropriate distance, I would think the BA12-3 might be closer.
My point is that this little 10-2 is very clear and even (for a bass cabinet and not a reference monitor) with little, if at all, coloration.
For gigs I would always use two BA10-2 (again unless it is a small rehearsal or some kinda acoustic/living room jam thingy
