The only time I go with S30V is when a particular knife I really really want is only available in that steel, the Kapara for example. As soon as a dealer exclusive Kapara in 20CV became available I got one and sold the S30V version. I like 20CV version so much better. Sure S30V isn't bad, it's pretty good even, but in my use I have to touch it up pretty much after every time I use it to maintain the degree of sharpness I prefer. As for K390, it's about the nicest knife steel I've tried. It seems to go on and on. One time I tried to cut some thick rope with my K390 Endura, didn't realize there was heavy galvanized wire hidden under it. The K390 edge was very slightly damaged, took about 400 strokes (<10 minutes) on the Sharpmaker rods to bring it back.