I personally wouldn't buy though a breeder when so many shelter kitties need homes.
thats how I feel also. there are just so many lovable , wonderful cats out there waiting for someone to adopt them!
as far a kitten vs. cat... its just whatever you choose when you go to the shelter... I have gone and just fell in love with a kitten, and other times the same has happend with an adult cat... like payitforward said, there are advantages to both.