>>1017884This plot is misleading. It looks as if the derailleur system has a constant efficiency of 94%.
This is not true. It depends on the state of the system (new, clean vs. old and badly maintained) and more importantly on your choice of gear.
Crosschaining will have negative effect on efficiecny as well as small cogs (less theeth - less efficient).
That doesn't mean IGH are more efficient (some actually are in certain gears), but it should be mentioned for a complete picture.
Source:
http://cozybeehive.blogspot.de/2012/01/factors-affecting-bicycle-transmission.html 