Quality/constructions? I don't think there are any new vs. old.
other than... "Catalina itself looked hard at its production methods. It changed the hull/deck joint at the stern to run it across the top of the transom and around the transom opening. This removed it from the transom/ hull perimeter, which is difficult to seal on the inside and is vulnerable to damage. note, I've never seen one damaged
A plate at the top of the compression post for the deck-stepped mast butts the step plate, so there's metal-to-metal contact from the butt of the mast right down to the keel, eliminating a prime source of old-boat maintenance woes. The mast wiring passes through a swan-neck standpipe to prevent water ingress. The chainplates, too, are new, with ball-and-socket joints belowdecks connecting to tie-rods, which lead to an aluminum channel laminated to the hull-liner pan behind furniture in the saloon and head."
I didn't think they got ripped all that badly.
Buy new if you can and want to afford it, buy used if you want to "fix" it the way you'd "really" like. you can get a really decent cat30 for up to what,
A new 309 will set you back 125k. (gotta love the sugar scoop)
We are not primarily on earth to see through one another, but to see one another through
Some people are like slinkies: not really good for anything... but you can't help laughing when you push them down the stairs