If you are looking for fully custom type, FARR KNIVES is a winner as well. I know there is a long waiting list for obtaining them, but from what I can gather it is worth it. Check them out at farrknives.com .
IT depends what your term "survival" knife means, that means different things to different folks. For me i want a knife that i can prepare food with, chop wood with, quarter/dress game with.... and yes defend myself with.
Ive used most of the knives listed above, and for me most are very inadeqate. The problem with most isnt the basic design its the lack of proper heat treat and wrong edge geometry (usually way to thick). Having a thick, obtuse edge makes cutting (the primary goal with any knife) more difficult than it should be.
Once you get a good blade with proper edge geometry, good heat treat, and good blade/handle design, it will seem to cut/perform like magic. Its kinda like shooting a box stock Springfield Mil Spec versus one that you have had built by Heinie, Yost, Garthwaite etc....
This is my current "go to" knife-
here is another of my favorite designs, this one made by Maggie Fikes-
If this is to be a survival tool, I would rather have a small quality hatchet and a nice 5" or 6" blade sheath knife. Weight would be the same, perhaps even less than a huge steel blade. Think about what it is realistically going to be used for in a survival situation.