For what? I went from Collaprible through all to type 4 formula (same as 5).
Collapsible was amazing on bw film, after it... just no name lenses. Well, type 3 is more less OK.
Starting from Rigid I was checking focus shift on M-E. Type 4 was worse, 3 is less, Rigid was the best. But Planar 50 ZM simply has none.
On digital Rigid was showing nice retro colors, but not too much of the retro and it was sharp.
Type 4 was best lens for color on M-E.
Type 3 is close to it.
I liked Rigid on C-41 and E6, it has very special sharp, but gentle rendering. Type 3 and 4 were also good. But less sharp.
Type 4 has crappy flare or vail.
I didn't CLA'd collapsible, it came cleaned from known good person. Rigid, type 3 and 4... I'm not impressed how they were made. Rigid is OK, but 3 and 4...
So, after using all of them, except APO and DR (same formula with Rigid), I would answer - collapsible for BW film, Rigid for color film and digital M.
PS. Here is thread on RFF, showing Clrons 50 focus shifts and vail is also known. So, it is not just me. Same for type 4 been sterile lens on BW film, but it is on rangefinder.ru