Why does the Nanobridge NB2-18 have half the speed of the RocketDish in speedtest.net tests today?

Details here:

I'm trying to figure out why the Rocketdish M2 does so much better in my application than the Nanobridge M2.

- Nanobridge = 18dBi antenna gain + 20dBm TX on channel 5 (-83dBm RX sensitivity on channel 5)

- Rocketdish = 24dBi antenna gain + 25dBm TX on channel 5 (-83dBm RX sensitivity on channel 5).

A friend dropped off a Rocketdish for me to compare to see why my speeds are dismal with the Nanobridge M2 and, much to my amazement, my speedtest.net speeds DOUBLED with the Rocket M2.

I'm not sure exactly what to attribute it to because the application 'should' be fine for the Nanobridge M2 (which gets -68dBm signal strength) - but the speedtest.net results are what they are.

Specifically, the TX/RX numbers in the side-by-side comparison in the referenced screenshot are vastly different (78Mbps/52Mbps for the Nanobridge M2 but 117Mbps/117Mbps for the Rocket M2).

What I'm not sure I understand is why the speeds double with the Rocketdish, given that the overall 3x signal level is only about 4dB higher (even with the 10x difference of 11dB EIRP).