pros of buying a young bird- get to raise it and expirence that process, you know your new bird from day one, the history is a blank slate no previous bad history, you have the choiceof what his behavior will be like, you pretty much decide this bird from day one.
cons of buying a young bird- sexual maturity is a pain if you dont know how to overcomeit, hand feeding is a very devoted matter of becoing a young parrot owner, There are many other animals needing homes instead of babies, you need to teach it manners and everything none of this was already taught to it.
pros of buying a 2nd hand parrot- I believe they bond stronger as you gave them a chance, if they are over sexual maturity you just got a huge relieve of your shoulders, You gave a animal in need a chance, 2nd hand parrots are great imo and they are happy with everything you give them, they are just glad to be loved.(all of my birds are rescues), the parrot you pick will be the way he is and baby can change throughout its life.
cons of 2nd hand parrots- you never get to enjoy the baby stage, possible bad history in previous homes, possible underlying health issues present(this usually isnt an issue, but could be), behavioral issues you may need to work with, but in the end this can become a pro because your bond will become stronger, they probably already have a name and you cant change that.
thats just some but i hope it helps you a little bit!
Thanks for your helpful reply, do you or anyone know of any good breeders in the uk or the best sites to try for preloved birds? I have tried a few sites but there doesn't seem to be many Hahns's available