I have used 16mm film for archival preservation filming extensively.  Until re
cently, it was difficult to view 35mm film on automatic readers (if not
impossible), so 16mm seemed to be easier to deal with.  I have found 16mm
to be satisfactory, provided the reels are not the 215' ones preferred by many
commercial vendors- the film is so thin that it breaks and gets tangled in
the reader-printer mechanism.  However, some older folks who have used the
16mm complain that the print is too small for them to read.  Apparently
35mm has a lower reduction ratio, which is why it has generally been preferred.
Denise Gluck