Let me see if I can get this right. The Endura/Delica originals (with integrated clip) had either G-2/GIN-1 (same thing) or AUS-8 steel blades. The Endura/Delica II series had the ss handles, and AUS-6 steel blades (a step down from the GIN-1 and AUS-8, in terms of carbon content). On Spyderco's steel chart, GIN-1 comes in at 0.90 % carbon. AUS-8 comes in at 0.70 to 0.75% carbon, while AUS-6 comes in at 0.55 to 0.65% carbon. The Endura/Delica '98 series (the current version) has ATS-55 steel, a step up from all of the above. Very similar to ATS-34, but with less molybdenum. Specially made for knife steel. 1.00% carbon (versus 1.05% carbon for ATS-34), again according to Spyderco's steel chart.
I would prefer the ATS-55 over any of the other Endura/Delica steels (well, unless you are REALLY worried about corrosion resistance), and would prefer the Endura over the Delica if it were to be my only knife.
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It's just a ****ing staple!
Outlaw_Dogboy