Preface with: I was long a fan of CDBI and would still use it for simple scripts like an an inlined SQLite CGI or such; the last time I did use it was for a standalone poll script.
While you say, "Mature and stable code," for CDBI, note that it has a few times been unstable with minor version to version changes breaking compatibility.
The results set stuff for DBIC is very powerful. And though the syntax is harder to master you will find that anything non-trivial with CDBI starts to require contortions, redundancy, and spaghetti. DBIC is a much deeper/cleaner design and much less likely to let you down on the edge cases that real sites/projects are riddled with.
Also, it's been awhile so I'm not sure how true this is now but in the past CDBI was quite a bit slower. Speaking of which, if speed is important, Rose is the speed winner.
Update: DBIx::Class beats Rose on some metrics now (there was a huge refactor in 2013–2014). I would no longer consider using Class::DBI for anything at all.