I don't have "lots" of knives but it seems all the different locking mechanisms are a cure for a problem I have never found. My old Buck 110 has never collapsed on me, nor has my Boy Scout knife, for that matter. I do tend to use tools in the matter in which they were intended though. I now have been carrying an Al Mar with a liner lock for about eight months and it works as well as all the other designs.
Kraton rubber on the scales of a pocket knife was stupid, hard to get out of the pocket and would not stay glued down either. Other than that they all seem to work well enough, like paint color on the car, get the ones you like. As far as steel goes I'm back and forth on toughness versus ease of sharpening. Tough steel seems to chip too easily, and I don't like carrying a steel or stone around all the time either. So when I'm away for a while it is toughness, around the house and near a stone the softer knives see duty.
The search for perfection is the reward, not the finding of it. I've used that old Boy Scout knife to gut rabbits and deer and to scrape gaskets from water pumps, and cut rope. I suppose I could have gotten by without another knife, but what fun would that have been?