Greetings,
I don't think there is really one truly perfect knife, for survival, or any other task unless it is very, very specific (like paring or something). I also don't think most folks outside perhaps the the active duty, deployed military purchase a knife with true 'survival' in mind.
Specifically, what do you mean by 'survival,' ie type of survival and where? For 99% of people, they normally purchase a knife with a general intent, be it self defense, utility, kitchen, camping, etc. Not 'survival.' Put another way, most don't buy a knife with the idea they're gonna go 15 miles up the trail, alone, where they have no cell coverage, break an ankle, right before dark and in the rain when its 40 deg. outside. To me that's a plausible kind of 'uh oh, the brown stinky stuff hit the wind generator' type scenario.
So you tell me, in that scenario, what would you rather have? A compact convenient little folder or a something with a little more capability? Truth be told, if you're smart, know what your doing and with a bit of luck (ie there's a great natural shelter nearby), you might be able to get out of that scenario if you do proper things regardless of the knife, but your chances might go up a good bit if you have more capable tool(s) at your disposal.
Whenever I hit the trail for more than anything other than a short stroll down by the river, I take along my go-to hard-use field blade...the Busse NMSFNO in a SpecOps sheath with a small folder, fire steel, and other gizmo or two in the pouch. I've also gone to keeping a very compact/lightweight (ie cheap) space blanket held down by the velco flap at the top of the pouch. The blanket is hardly my first choice if I got stuck in the woods, but its part of the knife kit (at least at the moment), ready to go, and always with me. On a cold wet rainy night, it would probably be worth a 1000x its weight in gold.
I figure short of being severely injured (unconscious, completely immobilized, etc), I could make it through a night or two decently with those tools in all except perhaps the very worst weather.
So I guess that's my answer: Busse NMSFNO-- 8 x .25 inch blade, ~13 or so inches over all, full tang, extended pommel, convex edge, protective coating. Paired with with a small folder.
But if I was going to be truly 'surviving' outside of normal inhabited areas, along with the NMSFNO, I'd probably want a saw and perhaps a hatchet/axe, depending on what else I'm doing and where I'm at.
BOSS