(An aside comment: If I'm on a desert island and I would need to depend on my 2 knives for survival, they would not get "MUCH abuse." If my life is on the line, my tools are being protected and used in such a way that I ensure they stay safe and functional. "Hard use" knives are an odd modern creation. Now that most folks in the industrialized world rarely have to depend upon knives for survival, there seems to be a fixation on destroying such tools and having tools that can survive the artificial abuse we contrive to throw at them. I doubt you'll find many folks in the more rural parts of the "third world" subjecting their knives to much abuse, especially those who do depend upon them.)
I agree here with the "hard use" view. Traditional knives are almost always stick-tang and for early folders, slipjoint. These worked for thousands and hundreds of years, respectively, and the people who used them depended on them, unlike hunters, backpackers and campers today, who may use their knife for a week at a time to needlessly split tree branches and cut para-cord. If their knife did happen to break, they're perhaps a day's walk away from a vehicle or other form of civilization. However, usually a knife isn't even needed when camping or staying out of doors today, (unless game needs to be cleaned, though even then there are some non-knife methods that may be available), and only used because one wants to bring it along and use it.
If I was stranded and had to depend on what tools I had with me, those tools would not be abused. The tasks that I would use a knife for would be clearing groundcover and preparing firewood (with a machete or axe), constructing a shelter, cleaning fish/game, carving spears, cutting fiber, making traps, etc. none of these require an especially thick blade in a "super tough" steel. Though it's always nice to have peace of mind, and I'm not saying that anyone is wrong, I cannot think of a task I would use a knife for that would likely damage it, (though it's always possible), and I wonder what tasks some are thinking of when they are advocating "hard-use" knives.
That being said, if I could choose what to be stranded with it would depend on where I was:
For an arctic locale, I think a mid-weight axe (if this counts) like a Hudson Bay Velvicut from Council would make the best fixed option:
Or, if an axe is out of the question, a leuku would be a nice in-between of fine carving ability and a larger workhorse:
For a bit more of a modern, full-tang option, an Enzo Trapper, in O1 for ease of sharpening. The Spyderco Bushcraft also looks great, though I'm not as familiar with it:
Plus a comfortable folder, like my Mini-Grip M4 edition coming soon:
I wouldn't normally choose a folder, but my reasoning here is, if the Axis lock fails, I can shim it up with a small piece of wood or some other material, effectively making a fixed-blade out of it. The arctic setting means (for me) a larger emphasis on fire and thick shelter, thus an axe or saw is top on the list. Also, food is paramount, given the relative abundance of water vs. the scarcity of game. This means trap-making and spear carving (for possible fishing) are important, as well as fire preparation. Thus, "bushcraft" knives would be my choice for their focus on ease of sharpening, comfort, and wood-eating Scandi grinds. Rust is a non-issue due to the scant humidity, thus carbon or tool steels in all of my choices.
In a tropical setting, I'm not too concerned with rust, at least in my fixed blades. I'm not of the mind that rust will not happen, but in my experience, it does not matter as much as people make out, at least for fixed blades. With this in mind, I think the Svord Kiwi is the best all-around machete out there for the money. It would be my pick for a fixed blade:
Of course, Tram Machete's are just as good in the end, if a bit thinner (some may prefer it) and with less F&F. If I had to take one, I wouldn't mind it.
For a folder in a tropical setting, I'd have to go with something stainless, because though rust doesn't affect a machete very much, it can cripple a folder fast. While a Salt is the obvious choice for zero maintenance:
I would feel just as good with something like a Native5 for it's great ergos and simple lockback:
My reasoning here is a machete can handle everything I'll need to do for a light shelter (bamboo), ground clearance, gathering firewood (which will hopefully be mostly driftwood and saplings), and making spears for fishing. The folder would just be used for cleaning fish and generally small tasks. Of course, I would prefer a stainless Mora to any folder out there for this, but the question was fixed and folder.
I may think of a better lineup, but as of now I think any combo of these tools would be my picks.