If I'm in a survival situation in, say, the Rockies and need to build a shelter I'll be looking for deadfall (I've never spent any time in Rockies really so I don't know what it's like, but I do know that in the Sierras if I'm below the tree line I can find deadfall). What I can't do with deadfall I can easily cut with something smallish (pine boughs and saplings). If I can't find deadfall because there's too much snow and I need a shelter, I'm going to build a snow shelter. If I need to burn a large log for warmth I can create a fire with smaller stuff and feed the log in, but my preference is to find nothing larger than wrist thick so it's easy to carry back and easy to break apart between two rocks or two trees. If we're talking really long term here, I'd have an easier time cleaning fish and game with something smaller than a junglas and I can make a stone axe (which may or may not be better at chopping down trees that something like a junglas).
I'm looking at this from a "my plane crashed and I somehow fell out of it with nothing by my knife and need to survive the night so I can improve my situation tomorrow" standpoint. Or maybe from a "I'm out hunting and my pack, rifle, and everything else but my knife just slid down a cliff and weather is coming in fast and it's going to be well below freezing tonight" standpoint. I'm NOT looking at this from a "I've decided to take nothing buy my knife and start a new life out in the woods right now" standpoint.
To each their own, I think the SRK fits the bill (along with a lot of other stout 6ish inch bladed knives). I like big knives, but I don't like carrying them.
I mean, don't they teach SERE school with some sort of 5 inch pilot survival knife anymore?