I can give you an example of my boat (35 year old H31) vs. an early 2000s H310 in my marina, so that you can decide for yourself what the differences are.
1) You buy a boat because you fall in love with her. It could be the layout, the sailing capabilities, anything that makes your heart stop. In my case, I like the layout and the sailing characteristics (and the price, of course).
2) After 35 years, the hull does not look as nice as on the younger boat. You can polish it to perfection but it is becoming too expensive relative to the value of the boat. This is even more noticeable with the deck. The non-skid is worn out on a few places, while the younger boat looks fresh and shiny. Can you fix it? Yes. Is it worth it? No.
3) Inside you have teak, younger boats have other materials. The older boat, especially one that was not super expensive at the time, shows its age. The sole is worn, some of the joinery is falling apart. Again, it can be fixed but not worth it.
4) The bottom you paint every 3-4 years, so no difference. The mast, standing, running rigging, sails - no difference. Systems, no difference. Any boat that you buy you will be refitting every 5-10 years based on your use and preferences. Similar to how often you renovate your apartment.
5) Engine, the older boat may need a replacement, mostly because 30+ year old engines have difficulties in obtaining parts. I replaced mine at age of 32 or something. My boat happens to have fiberglass tanks, etc. Other boats have tanks that corrode after a while. If you get into tank replacement, water heater replacement, etc. where you have to disassemble half of the boat, it becomes increasingly not cost effective.
6) Another consideration with 30+ year old boats is how much longer you would use it. For example, if I were to replace the standing rigging now, the new rigging would be good enough for another 15-20 years. The boat will be 50-55 years old at that point. It is probably not worth it. Again, very similar to having an old car and deciding to fix it or buy new. At some point it just does not make sense. I think I may sunset the boat next 5-10 years.
SV Pizzazz