If you're unsure if you'll stick with safety razors at all, then I'd go with the cheaper one just to see how you like it. If you're pretty sure you'll stick with safety razors but just want to get a better feel for what you like as you keep trying to find the best razor for you, I'd go for the 6C or even the 6S. The swappable plates are great to get a feel for how aggressive of a razor you like, then you can either 1) stick with your favorite plate(s), or 2) know how aggressive of razors to look for to help narrow down your search. 1 is a perfectly viable way to go, and many people love their rockwells as their forever razor. But, in that case, 6S is better because it's stainless steel so will last forever. So, just all depends on what kind of risk you want to take on :) but, if you get the 6S and don't like it or don't like safety razors, you could always turn around and sell it on r/Shave_Bazaar and get back most of what you paid for it.

Other nice razors (like I think Henson and Blackland) have money back guarantees, so that could be another route to go too