Is the energy spent climbing stairs different from a ramp, even though both accomplish the same task of transporting cross two points.
In a stair you bring yourself up a stair height and then stop and re-do the climbing process. So your momentum starts from zero and ends at zero at zero for each climb (perhaps you have very little residual momentum at the end of each climb). In a ramp, you are more "walking" than just climbing, so carry a forward momentum. Does this help climb better?