as a matter of physics,
a shorter crank will give smaller radii of the stroke=less movement of the knee,
however, using a shorter crank also means more force is necessary to apply the same rotational torque to the spindle as with a longer crank,
(the moment arm is shorter, torque=Force x Distance from center)
when calculated out, those 5mm aren't too big a deal,
so if your dealing with a lot of hills it might make a difference
only thing i can say is try it out,
thats pretty much the only way to find out if its more comfortable