I agree that there's nothing to be gained by pulling on the upstroke. Pedal stroke improvements for me are in the 11 to 1 o'clock and 5 to 7 o'clock areas of the stroke, and I think clipless is very helpful there, at least for me. Plus, my big old feet don't fit in clips very well in anything other than cycling shoes anyway, and I find clipless way easier to get into from a dead stop than clips. YMMV.