Speed and efficiency I suspect

Targeting a propeller for both raw lifting capacity as well as speed is quite difficult. I suspect they have different geometry as well.

If you spin a propeller fast enough the tips break the speed of sound, from what I recall that knackers the efficency. To generate lots of lift a bigger rotor is more efficient (hence why helicopters have long rotoblades that don't spin at high RPM)

The longer the blades the faster the tips, which means there is a tradeoff between thrust and speed of the air being yeeted out the back

stealth