Heres a link to an article/review about the pentagon fixed blades:
http://www.themartialist.com/pecom/sogpentagon.htm by Phil elmore
Some info on the AUS steels from A. G. Russels website:
http://www.agrussell.com/knife_information/knife_encyclopedia/articles/steel.html
AUS-6 - AUS-8 - AUS-10 (aka 6A 8A 10A): Japanese stainless steels, roughly comparable to 440A (AUS-6, .65% carbon) and 440B (AUS-8, .75% carbon) and 440C (AUS-10, 1.1% carbon). AUS-6 is used by Al Mar. Cold Steel's use of AUS-8 has made it pretty popular, as heat treated by CS it won't hold an edge like ATS-34, but is a bit softer and may be a bit tougher. AUS-10 has roughly the same carbon content as 440C but with slightly less chromium, so it should be a bit less rust resistant but perhaps a bit tougher than 440C. All 3 steels have some vanadium added (which the 440 series lacks), which will improve wear resistance.
OK, now go to this link and scroll down until you get the table showing the different metals and their uses:
http://cutlerscove.com/kwg/knife-steel.htm
You'll notice that the last link indicates that 6A (also known as AUS 6) is probably the best general purpose metal, and it is the only one listed as the best metal for Fighting Knives. Lets be honest, the Pentagon Fixed Blade wasn't REALY designed to open letters or cut a stray piece of twine... You pull that knife out, you're probably going to stick it into somebody's heart or sever a carotid arterie - and that's precisely what AUS 6 is best for.
Thats my humble oppinion anyway!
Cheers!