I have two Session Steel Seydels, both relatively new so hard to say…I am also not a crazy hard blower, BUT I do on occasion play un-amplified with a bunch of people, in which case there is no choice but to blow harder to get some volume. So of course you may have to wait a year or more for me to say whether they are holding up well.
I will say that the C has pretty comparable volume/projection to a Special 20.
The action, that’s a tough question because I got the C harp set up for overblows/draws by Greg at 16:29 so it was not “out of the box” like my Sp20s. The other Session Steel I have is a Low C so that just plays different since the reeds are bigger. I do think it plays well and once I played with the low reeds a bit I get all the bottom bends. Fun thing about low harps is the blow bends up high are really easy and sound sweet.