1. What are pros/cons between liner locks vs. axis lock by Benchmade.
Liner locks are inherently unstable. Only the best designed and manufactured are reasonably reliable. They are popular because they are easy to open and close one-handed and they will hold up real well under ordinary working conditions.
The Benchmade axis, like the REKAT rolling lock, and the old Gerber bolt-action, are much more reliable, but pretty much restricted to the specific manufacturers. Many lockbacks are so strong, they are almost fixed blades.
2. What are pros/cons of different type of metals for blades?
Steel may be (high-)carbon, which will tarnish unless cared for properly which you should do for all tools anyway! Carbon steel generally outperforms stainless, in toughness, edge-holding, resharpenability. (Where did THAT word come from???) Stainless steels are less easily corroded.
Titanium is difficult to work and very difficult to harden to as good an edge as any steel. It is non-magnetic, so it gets chosen for demolition work, for example. It is light and tough, but not a first choice for a working daily carry folder.
Several cobalt alloys make excellent knives, since they can be made to cut well, resharpen easily, and corrode NEVER. OK, not never, but not in your lifetime. Dendritic cobalt, talonite, and stellite are the ones youll read about here. They are a pain to work, and tend to be rather expensive. Maybe not a first knife, but definitely worth keeping in mind. (Youve got to check out David Boyes dendritic steel and dendritic cobalt and Rob Simonichs work in talonite.)
By the way, knives are also made of different composites, like zytel, G-10, or cheap plastic, which are generally known as handle material. These are usually stealth knives metal detectors wont spot them. Ceramics are also useful, but not in the field: they are brittle, but they are SHARP
3. What are pros/cons of different handle materials. Looking for something that doesn't get slippery when wet/damp.
Im gonna pass on this. Knifemakers generally do not put slippery handles on their knives, although some materials are more comfortable than others. But handle shape has a lot to do with this, too.
4. pros/cons of straight grip design vs. contoured to fingers
This is a classic case of what works for me may not work for you. It isnt always possible to guess from a picture, and it isnt always easy to find a store nearby where you can pick one up and try the grip. You will also find that the human hand is a flexible gripper, that can adapt to a variety of handles.
Dont forget, for a working knife, you may want one kind of grip, a fighting knife another. A small gentlemanspocketknife may do fine with a simple, sleek shape.
5. Any overlooked suggestions? Things to look out for and avoid?
Dont buy knives with multi-colored wood handles.