From a commenter under the video:
Summarized the measurements, with rough timestamps:
Stock blades (6:43): 1 m/s, 64.3 W,
simple airfoil (7:55): 0.8 m/s, 66 W
modern airfoil (9:12): 1.2 m/s, 64.5 W
stock motor no blades (13:49): 53.8 W
BLDC motor no blades (16:24): 8 W
BLDC stock blades (18:27): 1.8 m/s, 59 W
BLDC stock blades at reduced speed (19:35): 1.0 m/s, 27.3 W
The energy efficiency difference is insane - 8W vs 53.8W at no load means BLDC motors use about 85% less power just to spin, which is why my electic bike can go so far on a single charge.
DC motors will tend to be optimal only at a set speed/torque whereas BLDC motors do need a microcontroller to be driven, but are able to optimize the flow in a much wider range. Coils in a DC motor are basically ON or OFF whereas they can ramp up in a BLDC depending on the speed.