I think we need to understand the definition of efficiency in this case.
Defining as simply a measure of work overcoming losses in the gear mechanism does not take account of work to overcome weight and rotational momentum which is significantly larger than for a derailler system. These are exaggerated during climbing.
>> The quick shifting and even gear steps of the Rohloff are also more likely to work in your favour
Disgree. The even gear steps are fairly large steps compared to many sporting derailler setups.
Quick shifting ? Nah. Negligible at best. I'd say deraillers are quicker: in my personal experience I ease off more changing on the rohloff than I do on deraillers.
I was talking about comparisons with a similar type of bike. My Rohloff is on a Thorn Nomad so comparable to derailleur MTB tourers like Surly LHT, not a schmick Cervelo. The weight difference is well over-stated - apart from super-light racing gears, when you add in all the component changes in conversion, it is probably less than 200g difference, if that. When I built my Nomad up, it came out to exactly the same weight as the Giant Sedona MTB tourer it replaced, even with the heavier Rigida Andra 30 rims (just using a basic scales).
Gear steps - also talking about similar gearing set-ups ie. touring/MTB derailleur and wide-range cassette. The Roohloff was designed to replicate the typical MTB range - at the time of design it was comparable to the 8 spd (later 9 spd gave a slightly wider range possible using the 11t).
Shifting speed - my personal experience looking at Rohloff compared to a touring range is the Rohloff is noticeably better shifting, especially on the down-shift (except for 8-->7 of course). Derailleur gears you have a lever throw, with a lagging chain shift to the lower gear; changing up is quicker. With the Rohloff it's just a twist and the change is always instantaneous - up or down. A nice 11-25 road cassette will of course shift quicker, but Rohloff was never intended to be racing-oriented gear.
Just my experience.