Will :
The only blade with which I could tell no significant difference between the first cut and the 100th was a Stellite 6K Gerber hunter, which was one of a limited edition of 200 knives commissioned by Deloro Stellite in about 1995.
Out of all the cobalt blades I have worked with (Talonite stock removal and forged, Dendritic Cobalt, Stellite 6k, and some unknown variant {chisel marked simply as Stellite]) the 6K knife from bladeforums members Will York and Cobalt (same blades from Gerber) are easily the most impressive materials wise.
The Dendritic Cobalt blade from Boye has a much more efficient cutting geometry, no surprise there, but it a little too brittle and weaker than the 6K as well, simply because it is cast. Dendritic 440C is much more durable, but still not as durable as Stellite 6K.
Of course Dendritic 440C is not near the top in terms of durabilty when it comes to high end steels. There are many steels which are as durable as 6K, moreso in fact and are stronger as well. Not as corrosion resistant though, and they will wear quicker in "dirty" work, gritty materials, rock, metals, scraping, that kind of thing.
I have loaned some blades to friends who are divers and it is rare to get them back with a functional edge on them because of the poking, scraping and prying that it done on materials that are much more abrasive than what I usually cut which is wood and rope and such. I think I will loan them my Talonite blade later on and see how it fares.
The thing that I have been tossing about lately is getting a decent large 6K chef's knife. It has a very nice set of properties for such use, near ideal in fact. Cost is the only thing though. If you compare it to say a 420 (mod) blade from say Phil Wilson, which also has very good strength and toughness, how much of an advantage are you getting for your money, which I assume would be significantly different.
It would be interesting to see a long term use report and verify what if any is the functional difference in the "lifetime" of both blades.
-Cliff