I've been proudly using very small cabs for years. First 8", then 6", mostly both together. B&C speakers, homemade design with ports.
My personal opinion is that bass heavy cabs are nowadays generally useless. Small rooms, the lows just generate naturally. Big stages, there's always PA with monitors. The real task for the bass cabs is to achieve clarity, in pitch and dynamics. This took me many years to find out, and I repeat that it's only a personal opinion. I play jazz to pop.
Nowadays I'm using 1x12" Eich XS cab, which is light and easy to carry, and sounds really cool. The main difference between 6" and 12" in my opinion is not in perceived volume much. Rather, the important difference is in coverage. While the 6" projects in a not too wide cone, the 12" can be heard almost from anywhere. With 6" I had to be smart about cab placement, which taught me a lot about how stage sound really works. 12" is much more tolerant in that matter.
Unfortunately, there's no way for you to know in advance which cab will project ideally. I heard 12" or even 15" cabs which were poor in that matter. The best way to find is to try another's cab on a stage or in a rehearsal room.
