Before getting a Benchmade 555 Mini-Griptilian, my only experience with 440C was the Spyderco Meerkat.
I liked it on the Meerkat but I loved it on the 555.
So much so that I later bought a 550 (which I gave to my brother-in-law because the oval hole did'nt work too well for me), and then I bought a 556 and a 551.
And a Boker Titanium folder with 440C.
440C has become one of my favorite blade-steels.
I find that I can get the knife extremely sharp with very little effort, and it keeps its edge for a respectable amount of use.
I like it better than AUS6, AUS8, GIN1, 440A, ATS-55, and even better than ATS-34 and 154CM.
The only blade-steel I like better is Spyderco's VG-10.
I don't have any real experience with S30V however.
But remember, blade design matters more than blade-steel.
The 551 and 556 are awesome cutters with an exceptional blade grind.
I think you will like the 551.
Good luck,
Allen.