So, pros of a cadet are youth, fresh faced, blank canvas ready to be moulded by the airline, rich, no undesirables, smart, trained specifically for the role etc ctc etc.
Cons, very limited hands on flying with 0 experience to fall back on even when they have 5000 hrs heavy IFR time, almost a total lack of charecter building life experience.
I really don't think it's the dichotomy that you are suggesting. The airline training programmes I've seen all value life experience; all suggest flying experience is advantageous; and all take people from a variety of age groups and backgrounds - including parents with young kids.
Also, in what way does having 5000 hrs heavy IFR time constitute zero experience? Of course a lot of the flying is done by autopilot, but a lot of it is hand-flown too. On top of that there are regular simulator proficiency checks where real emergencies can be practised (ironically something you can't do to the same extent in a C152 or PA38).