My one experiment with 175mm cranks on a road bike was uncomfortable. The small difference in pedal circle (10mm) was quite noticeable in its effect on cadence. FWIW I am height challenged at 65" and the cranks and pedals were the same make on both setups. OTOH I never noticed the 175mm cranks on the ATB, but the terrain variances off road are so extreme as to swamp any cadence changes. Recumbent riders who are torque challenged have advocated shorter cranks for years to facilitate higher cadences.
It is easier to spin short cranks and they reduce the torque the knees have to supply.
Steve