Aluminum is almost as corrosion resistant as titanium. Some people don't like metal handles, though, especially in winter
or if the knife is going to be used for cutting up animals or food, which might make those handles too slippery. I generally prefer metal.
G-10 may be the best of the plastic-like materials. It was originally developed for circuit boards and is highly resistant to corrosion, acids, electricity, blood, sweat, and tears. But Micarta is also good, and Zytel or F(iberglas) R(einforced) N(ylon) is quite serviceable, too, although some consider it cheap. Stabilized woods, impregnated with preservatives, are practically as durable as these artificial materials.
154-CM is a recent "super steel" and the American twin to the highly regarded Japanese ATS-34. Its properties are now well known and its heat treatment is pretty well assured. Yes, S30V is the "latest and greatest" but that doesn't invalidate the quality of earlier excellent choices.
How a company heat treats its blades, what the thickness and sharpening angle is, and how the edge is shaped are all at least as important as the actual steel used. In fact, a good, cheap, old fashioned high carbon steel will intrinsically outperform all but the very most expensive of the new stainless steels. It just rusts more easily, which reasonable maintainance can avoid.
Ranking locks is an unnecessary enterprise. Many are more than good enough, holding up against more force than the human hand is ever likely to apply. The frame lock (monolock) is extremely reliable. So is the axis lock. The axis lock is more fun to play with. Lockbacks are almost foolproof. Slipjoints themselves are perfectly safe if the user only remembers to cut with the edge and not with the back.
The frame lock is a development of the liner lock, which when properly constructed is also reliable. The SOG arc lock, Cold Steel ultra lock, and Spyderco ball lock are all variants of the axis lock principle, which itself is similar to the old Gerber bolt action lock. But no folder lock is inherently as strong as a well made fixed blade.
