Two or four speakers?
Obviously four will be louder. But that might also mean that four can be played more conservatively to attain the same volume and they will be performing with a little less stress and distortion. When coupling more speakers, like two pair versus one pair, the speakers always seem to sum for a little warmer balance. Also, with the rotating collars, you can spread the dispersion for a wider field versus a narrow and beaming effect. Horizontal speaker arrays tend to have really bad off-axis cancellations at the upper frequencies. Fanning them out just a bit can help offset that effect.

David
Earmark Marine