420HC...least expensive, good rust resistance, decent steel for EDC knife.
154CM...better edge holding, a little more prone to rust.
D-2...not quite enough chrome to be considered stainless, great edge holding, requires a little more care. Great blade steel, IMO.
Talonite...cobalt based alloy, will not rust. I have no personal experience, but from what I've read, the stuff just keeps on cutting after losing its hair popping edge. Most expensive.
Paul