I've ridden bikes fitted with 140, 165 and 170mm cranks. I can still produce power effectively with either of them, but the 140mm set feel noticably different (the 165's are virtually identical to the 170's). If you are a fast cadence rider, turning a shorter crank with a lower gear may be easier than turning a long crank with a proportionally higher gear (same gain ratios) but I doubt you'll notice a difference. We all climb the same sized staircases and ladders without thinking about it