I use the 65 and 105 on mine the most. Love those lenses.
Changing lenses, I often forget to switch the parallax indicator on the left side to the new focal length.
I like the prism or porrofinder for tripod use only.
Edit: Late on the comment about parallax; had intended to post it earlier...but 2F, the c330's indicator will show with any lens you have mounted, but won't be accurate unless you turn the ring on the left-hand side to the appropriate focal length setting. (it's the rim surrounding the lock/unlock dial for lens changing...) I'm sure the often-referenced Mamiya site and manuals can show exact details.
The C220 uses etched lines on the groundglass to indicate parallax, so no such worries there, but also no great accuracy.