Right, but the actual % efficiency does matter. Derailleur and IGH achieve easily 90+% efficiency with low maintenance. Is this in the same ballpark? 80% ? 60% ?
Also the string will definitely pick up grime off the roads, especially when wet, so efficiency will almost certainly drop as a result.
the FAQ says the string is technically more efficient but in practice they are both extremely efficient when properly maintained so the difference is academic. They don't mention losses when the string is wet or dirty so I'm not sure about that.
Also the string will definitely pick up grime off the roads, especially when wet, so efficiency will almost certainly drop as a result.