As simple mechanical view, reeling power comes mainly from torque that creates by reel handle.
More precisely, the distance between knob and rotating axis directly proportional to torque.
Torque = distance(r) x force (your muscle)
I've never seen closely, but it seems reel handle length between accurate ATD-30 and 50 seems almost the same.
If this is the case, reeling power of these two reels is same or ATD-30 may be higher because it retrieves less line with the same amount of torque...
With having said Bla Bla Bla, I am wondering if anyone tried to put custom longer reel handle ?
Of course, this may add more stress to reel... but longer handled reel may provide same power to weak muscle man as stronger muscle man reeling with shorter handle.. Stress to reel is about the same.