I don't think that many would choose a 1985 Oyster over an identically sized 2006 Grand Soleil when both cost the same.
On the contrary I think the educated buyer would choose the Oyster even if it was an 85 over a 2006 Grand Soleil every day of the week.
Comparing parts and pieces such as a macerator or water pump gives me no piece of mind. I owned a brand new boat in 2005 and still had to replace parts even within the first two years such as a windlass motor, a water pump and a head pump.. Older boats usually have the bugs worked out new boats don't especially if they have been "lightly used".
I would not be caught dead buying a Grand Soleil over an Oyster if I had the opportunity. I'm of the opinion that steel, even galvanized steel, we've all seen older galvanized boat trailers, has NO place as the structural backbone and support for a 45+ foot fiberglass boat. This galvanized backbone is a COST savings approach ONLY. If they were really interested in quality, longevity and rigidity they'd build a boat the way Hinckley does with directional Kevlar & Carbon Fiber cloth and the SCRIMP process using only epoxy or vinylester resins. Grand Soleil makes NO mention of the type of cloth used or the resisns..??
Of course that would add a few hundred thousand dollars to the price of a Grand Soleil and with good reason...
I'll buy an old Steinway grand piano over a new Yamaha grand piano every day of the week and I'd still buy an 85 Oyster over a Grand Soleil every day of the week. There is a REASON why an older Oyster is the SAME price as a NEW Grand Soleil and that reason is LONG TERM quality..
Keep in mind these are just my opinions after having worked on and sailed many production boats and high end boats. A good survey by a KNOWLEDGEABLE surveyor will tell you more about a boat than what model year it is and you can't paint any boat with a broad brush, by the year it was built, only.. Parts are parts and they WILL fail on a 2006 model just as easily as they will on an well maintained and kept 85 model. Thinking parts won't fail on a newer boat is.... well.... perhaps ....delusional.
I had more parts fail on my brand new 2005 boat, in the two years I owned it (working the bugs out), than I have had fail on my well maintained and kept 1979 since I bought it.... My 1979 is a far better constructed vessel than my 2005 was and even at 29 years old and 40,000 plus km's under her keel she is showing less wear and tear in terms of structure, stress cracks and the like than my 2005 did after only two years....
I'd suggest sailing both a 1985 mass production boat and a 1985 high end boat, of similar length and displacements, in 25-30 knots before you even consider buying.. I'll say no more on this because I know the differences, and you will too, after a test sail on similarly aged boats of differing qualities...