I have B.C.B. commando saws in my Ritter S.P's. Correctly employed they are a worthwhile addition. The trick is to cut a length of green wood. Notch it near each end. Bow it and slip the wire saw on to the notches. Which gives you a bow saw. Treat it with respect and don't get ambitious.

I also pack Survival Inc chainsaws. They are an absolute must for a pocket survival kit. I have tackled tree limbs of up to 12" thickness with them. However 6" seems to be the normal practical limit.
Gerber or Granfors-Bruks folding saws are better for limbing branches and cutting firewood, snow blocks etc.

So: If I want to demolish a tree(s) for whatever reason, I would go for a pocket chain saw. If I was building a shelter, then a folding saw would be my prefered choice.