Yes, you can bring more of your body into the pull, I should have clearified what I mean. The folding saws are more efficient because they don't require your shoulders or back. You can attempt to bring these into play by pushing down hard on the blade but the increase in performance usually isn't worth it (depends on who you are of course), as they are designed to run very light as the teeth are set at very acute angles and they cut very aggressive with little to no draw load. For example cut through a seasoned 2x6 in < 10 s, and this is with little force, ie. you can do this at pretty much any body position.
For example yesterday I spent an hour trimming some Alder bushes, the main sticks were 1-2 inches thick and the stalks up to 1" thick. With a #60 Felco, it was as simple as using one hand to move the other sticks out of the way and giving a couple of pulls on the saw and then flicking the stick over the shoulder with the free hand and then repeating the process.
As I had one free hand, and a saw with took up very little space it was trivial to work in a very heavy ingrowth situation, here a large bow saw would have been useless. The chain saw blades styles would have been much less efficient as the small wood was flexible and would have just bent under heavy pulls and the time it took to actually loop the saw under and around them would have had it cut already with the Japanese saw (which also cuts, plastics, ropes, fabrics, cardboard, etc.) .
Consider limbing, felling and bucking a small tree, 4-6" with both types of saws.
The bow saw excells at felling (once you make room), and bucking (but you have to have a way to make the log stable), and is crappy at limbing.
The japanese saw will keep up with the bow saw at felling, but will fall behind if you cut high on the tree and thus can bring your upper body into it. However at bucking, if you have to hold the log still, the japanese blade will easily keep pace, and requires less effort to use. At limbing there is no contest, trying to start a cut on a small diamter branch with a swede saw blade is difficult as it manuvering the saw around the branches.
The small chain saw blades require less space in that they are much thinner, but require *much* more force to drive than either of the above two patterns, you are also constrained to two hands unless you make a bow, and in this case you are now using a really inefficient bow saw. At limbing, better than a bow saw, but many times slower than the folding saw which just zips from branch to branch.
For any kind of survival / emergency situation you want a tool which needs the least from you to work, and thus one handed with light effort. I recently split my index finger on my left hand open from the first knuckle to the third (eight stitches), I could still easily use my folding saws, trying to use a two handed one would have been very difficult.
Consider shoulder, back or other hand injuries. For you to not be able to use a Japanese saw you would need to be so weak you could not lift a can of pepsi, but the others are more readily disabled.
They have their uses though, I like a bow saw for serious bucking (though I have not tried any of the large japanese pruners), and the small chain saw blades are very packable so you can even carry them in your pocket in a small tin.
-Cliff
