well lets talk about efficiency; the ratio of output to input of a given system. Taking a small steep onto a escalator then being effortlessly lifted up 2 stories is far more efficient, for a person, than walking up said stories. However if you include the power of the escalator in the system it is probably more efficient to walk. But remember the escalator will continue to run if you walk on it or not. So the escalator power cancels out across the equations and you are left with the energy you used personally to walk up the stairs. So it is more efficient to take the escalator, however if you are talking about time then that is a different story. If you went up the stairs faster than the escalator you would have to solve this equation.
Energy Used Taking the Escalator = (Time on escalator)*(energy used by esclator)+(personal Energy)*(Time on escalator)
Energy Used By Taking Stairs = (Time on Stairs)*(...
holy shit there is a kid in a balloon thousand of feet in the air...
http://www.9news.com/news/article.aspx?storyid=125161&catid=339