ORIGINAL: Sport_Pilot
You don't make a double eagle with just your drive, or your approach, or your putt.
But are you after a lower score or a longer drive. The Cessna achieved a lower score with two engines on the same line. It isn't faster (drives the golf ball farther) with just one engine is it? If you wish to consider all things, then consider that the pusher receives disturbed air no matter what. The Cessna example actually does suggest something to that idea. Very disturbed air to the pusher really screws up the efficiency of the climb and evidently operating the front alone isn't as efficient as the rear alone IN A CLIMB. Disturbed air increasing drag appears to be a significant problem with a pusher. And that can cause problems. Be prepared.
Don't you mean effectiveness? Were we comparing fuel usage between front and rear engines? Unless we do we do not know which is more efficient. The front engine could be using much less fuel and thus more efficient even if the climb rate is worse. IMO many here confuse the heck out of me when they say something is more efficient when they should say effective.
OK effectiveness.
But efficiency is perfectly accurate. A more efficient aerodynamic package usually does whatever the pilot is asking better. For example, a cleaner trimmed airplane will have less drag and usually more speed. So the pilot backs off his power or allows the extra speed. If he backs off the power he'll probably get better economy (the term for efficiency in fuel use), but not always.
An airplane that climbs more efficiently (less drag) usually climbs faster. If it climbs faster with one engine out, that out engine's added drag is causing far less drag than whatever is hurting the climb rate when the other engine is the out engine. Is it efficiency or effectiveness? You're right, I should have used both words in spite of wishing to point primarily to the drag problem.
A wing that creates the required lift with less drag is more efficient. The P51 carried more weight faster than (pick another airplane) because it was more efficiently creating lift/drag. An airframe configuration (trim settings) that creates less drag and more speed or climb is more efficient but not always more economical.
BTW, running one engine versus two might be more economical as well. But economy isn't the issue.