Ah. An excellent question.
My selections are usually based on intended use. I have a number of standard cutting scenarios, and try to find knives that will fit well into these scenarios. Some scenarios cover quite a broad range of tasks, but some are quite specific.
Whenever possible, I look for a full convex grind. I prefer full convex grinds for pretty much all of my cutting. If I cant find a full convex grind, Ill try to find a knife with a convex grind on the edge bevel. I had to settle for the Busse asymmetrical grind when I placed my order. It wasnt optimal based on my personal preferences, but Im sure that the asymmetrical grind will do fine. If it didnt, I doubt that Busse would be so popular in the world of using knives.
Im not a huge fan of stainless steel, and love it less and less as I use it. I prefer a good carbon steel for rough use, and talonite for light use. I guess Im a man of extremes. I do still use some stainless steel knives, but only a few with exceptionally good designs (like the Sebenza).
If my knife is a locking folder, it darn well better have a VERY good lock. Id prefer no lock over a wimpy lock.
Comfort isnt as big a deal to me as it is to others. There are only a few knives in my collection that are too uncomfortable to use. These usually have badly shaped handles, which are just too small or oddly shaped for my hands. I equally prefer straight handles to ergonomically shaped handles.
Aesthetics are important to me, especially when Im around other people. I find that sheeple respond well to natural handle materials. When Im in the woods by myself, durability is more important.
Warranty is definitely an issue. I always look for a good warranty, and have done well so far. Ive never had a bad warranty experience with a knife company, but some have been clearly better than others. I look for manufacturers that not only see me as a customer, but as a future customer.
Accessories do matter to me. If somebody sells me a fixed blade, it better have a usable sheath. It doesnt have to be a custom quality sheath, but has to be usable. I did consider Marbles (whom Ive had excellent past experience with) when buying my last knife, but chose a Busse. Id rather keep my knife in an old shoe box than that crappy sheath that the larger Marbles knives come in. The standard Busse sheath looked perfectly usable, with many future custom sheathing options for the future.
Price is the smallest issue. I believe in spending good money for a good tool. I'm in no way a rich person. I'm just a civil servant. But I don't purchase ten cheap pieces of crap to do the work of one good tool.