sorry, I can't test hAP AC either
Few points:
1) do not expect some magical increase of speed when going from 2 to 3 chains. Especially when most of devices (phones, laptops etc) have just 2 chains.
2) It is true that 5GHz has much higher attenuation than 2GHz so it will give you less range (do not expect much signal behind a brick wall) but you can combine them and use 2 and 5GHz at the same time. Your devices can then either freely roam between bands or you can select whichever suits you best.
With 5GHz (AC - 20/40/80MHz), I can get average 280Mbit (~35MBps) which isn't much, but keep in mind thats RBD52G we are talking about - it is based on ARM and there is known issue with speed which might be fixed in upcoming releases. (although my current experience with 6.44rc4 does not show any improvement)
I am unsure whether RB962G (hAP AC) would perform significantly better. Maybe someone else can test share own observation
edit: difference between 20 vs 20/40 can be positive but also negative! it all depends on interference from other network and devices. If you have full 40MHz of free radio spectrum, it should increase your speeds. however, if there is lot of interference, it is actually better to use just 20MHz to avoid constant re-transmission (thus slowdowns) on extension channel. Similarly, choice of the channel is also crucial for achieving good speed.