I have both.
Get the f/3.5 version. It's not just the faster lens, but in just about all respects the better lens too.

And yes: the CF version is the same optical design as the C f/3.5.

Having said that the f/5.6 is less good, i'm in still the market for a good f/5.6 60 mm C lens. The one i have is rather tired, and i like to have a prettier (and fully functioning) one for my 1950s HB kit. So if anyone has one that looks good and functions o.k. ...
(By the way: the less good performance of that tired lens is not due to the condition of the lens. It is on par with that of the 1000-series era f/5.6 60 mm lenses (same optical design) i have too.)