Rust resistance is overrated. The knives used to pioneer America were all carbon steel, even before Lewis & Clark. What they did is carry all they needed for a transcontinental expedition, and knew they were going to trade with the indigenous peoples, to boot.
A four inch clasp and 6" "butcher" were about it, thin stock because they will bend, not break. They last for decades, look at the ones still popping up in yard sales and flea markets. Carbon steel does ok - nobody gives them to Goodwill, the bins are full of cheap stainless, tho.
As said, the edge geometry and blade shape are each equally important. Then comes the handle, and also, what sheath. A knife mislaid or lost in transit is significant. Having a backup equally so - carry more than one so you will have one. The gun forums point this out repeatedly, two is one, one is none.
That means better to spend the money on two carbon steel knives, rather than twice as much for a stainless. There is also the performance per dollar factor - a knife twice as expensive will never be twice as sharp, and keeping it that way usually means it's twice the work. Carbon steel is relatively easy to touch up compared to exotic stainless, and D2 is notorious for not taking a great edge.
It's why the militaries of the world use carbon steel in their "survival" knives - the extra expense of stainless isn't justified. And in third world countries where knives are used in primitive conditions, carbon steel is the standard. Part of that is economics, part the ease of making one in carbon vs. the high tech, expensive, and difficult methods needed to work in stainless.
For field carry, avoid using any material that is porous or can soak up moisture and hold it against the blade. It's why a lot of old knife sheaths were wooden, or even metal. Leather is too easily cut thru and wraps too tightly against the blade. These days, kydex is the preferred material. Note that most cordura sheaths have a plastic liner - woven materials are simply less expensive, which is no recommendation in sheath materials. Even bayonets are issued with fiberglass sheaths - not leather or fabric. Been that way over 50 years.
If this all sounds like I'm pointing to the ESEE series of knives, that's a good example. Experienced field professionals living in primitive conditions and trying things out generally come to the same conclusions, because it works better. It's not about "combat," as much as simply resisting the environment and being compatible with humans under duress.