154 CM is a generally superior steel to 440C. You can a Google search on "Blade Steels" and find lots of information.
154 has had a storied history. I was originally introduced for the blades within jet turbine engines. Later, it was found to be a superior blade steel, but there were problems in the finishing of the steel because it would "blemish" and not look proper. Don't know if this affected performance or not, but the steel fell out of favor in knifemaking. Hitachi went on to make a virtually identical steel in ATS 34 that became the most widely used steel by custom knife makers. There were other reasons why Hitachi's steel became so popular, but was a fine steel nonetheless. Eventually the problems with 154 were corrected and for several years it enjoyed the status of being included among the "gourmet steels" in the knife community. For a number of years it was the best blade steel made in the US. 440C never reached such status. 154 and ATS 34 declined in popularity with the emergence of CPM's S30V and some of the powdered steels like 440V and now even further with Hitachi's latest, ZDP 189.
440C's primary advantage is superb rust resistance. Although Microtech would stonewash 154 to improve resistance to rust for their knives used by underwater demolition teams and Seals - as in the Amphibian and L-UDT.
Probably more than you wanted to know.