Have you ever used a jet boil?
I bought a Soto windmaster and returned it after one trip because it easily used twice as much fuel per boil as my jet boils do.
I've used a buddy's jetboil, but not extensively enough to give hard data. I do think that the jetboil is more efficient at boiling water than most stoves, but there are a lot of variables. Heat exchange, wind, fuel output, which model (some jetboils do not have a regulator), koozy, container, altitude, ambient temp, ect.
The thing about jetboils that make them good are that they are an integrated system, so they'll basically get optimal performance out of the box. A jetboils formula is basically integrated burner + wind blocker + heat exchange + koozy + tight lid.
With my windmaster, I try to boil using my 1100 with a pot lid that seals better and has a wider base. The difference between boiling the same amount of water in the 1100 vs 750 is noticeable. I also use a reflective koozy that I made and put it on top while I boil water, which seems to help a lot.
The heat exchange makes a lot of sense, and I think that is a significant contribution to a "jetboils" efficiency. For me personally, not worth it for the volume I would give up and how well my system works together. I actually do use the full volume of both my pots if I'm eating more than freeze dried meals. Often I'll cook enough food for multiple meals and eat left overs. I can easily make 2 big/3 small meals in a 1100 pot and eat it throughout the day. I keep it stored in the 1100 pot, and still have the 750 to boil water throughout the day.
I realize I give up some fuel efficiency with my system in comparison, but the versatility more than makes up for it in my use. The fact that I can use an open fire with my system more than makes up for any efficiency loss with a stove, and the windmaster is plenty capable as a stand alone that I can use for pans/skillets/large pots without extra accessories.
I'm curious what the die hard, stove only guys do when they run out of fuel? Hike back to the truck? Drive to the store? Don't eat?