Depends on what you need to do.
Uutf just decodes the UTF-X encoding formats.
Camomile does a lot of other things but is stuck in a very old version of Unicode (unless things moved recently).
Some of these things (and more) can however also be performed by other small libraries that I publish and support the last version of Unicode. See “Unicode processing” on this page.
One notable omission from these small libraries is collation that you’ll find only in Camomile as far as I know – I do have a design for a Uu* library for that but lack a concrete project or funding to implement it (same for this Unicode text data structure).
Finally you may also want to checkout my OCaml Unicode tips.