Quote
o_lampe
If I had to choose between a 40mm and 48mm long 0.9° stepper, both rated 1.7A, I should choose the shorter one because of the lower inertia?
No, if it's for an un-geared extruder, choose the longer one. The ratio of torque to rotor inertia is probably similar for both drives. OTOH you should choose a 40mm 1.7A motor over a 48mm 2.4A one if your drivers can't deliver 85% or so of 2.4A.