I think the 6C is a very good razor. I get excellent shaves with it. And of course, it's very versatile having 6 different plates. The only downside is the head is a bit large but I have no problem with it under the nose. My preferred blade for the 6C is the Gillette Nacet.
I've considered selling mine to replace it with the 6S because I prefer stainless steel razors, but have not yet because the 6C does just fine.
The Rockwell 6C is a fine razor that is mild on plate 3 if you like that or you can try the higher plates if you like a more aggressive shave. I bought a used 6S a while back and need to sell the 6C.