The 180º sector is 13dBi where the A5 is said to be 14dBi, per panel.
Effectively this means that for longer range, the CPE will receive or send to the sector on 2 chains. MIMO 2x2 so you get an extra 3dB on top of the 13dBi which makes there for 16dBi.
Using the A5 on short to very short distance will probably be a better idea since here you still will have multi-path signals thus the 14dBi can still result in also 17dBi combined signal.
But on longer to medium longer distances, where remote CPE will have a highly direction 2X2 CPE the comparison probably will fall to the dual 180º sectors since 16dBi will be better then only 14dBi of the A5.
In very specific circumstances where an AP will be located on a steep slope of a hill with an A5 you are very limited. One side the signal burns the ground, the other side it will shoot in the sky.
Only with tow adjustable sectors on each side you can adjust for that.
Off course, 4X4 MIMO will never be achieved this way, but that is also not what I am after. An 250-300% increase in capacity in my network is already a game changer....