What is the practical difference between these two macro lenses? I have all of the black series lenses in 50mm, 80mm, and 150mm. I'd like to add the 120mm and am wondering what, if any real difference there is between these two. Older one goes for $300 and the newer is almost $700. Thanks for your input.
Well, not much difference apart from the extra stop and the obvious C vs CF difference, of which you are surely aware (if not, please see here https://www.photrio.com/forum/threads/hasselblad-c-t-vs-cf-or-cfi.134879/ - there is also a lot more resource on various places on the internet about this).
The two lenses are not of the same optical design. The 120 S-Planar is one stop slower, and will not focus as closely. It also flares more from what I have read (older coatings).