For years I'm meeting old GibSeas going strong and well. They old models were aimed at charter
market mainly, and it i well worth to remember that charter
market in 80's and even 90's was completely different than today.
GibSeas were built simple, but very robust and strong. They were designed to work for ten to twenty years in charter bussines, while today five years is maximum envisaged. I personally met number of GibSeas in good working order after twenty or even more years in charter business.
If You can find one built as a private boat and well kept up, I believe it can be very good buy. You can also look at first generation Bavarias. They were really great boats once upon a time, before Bavaria
went bankrupt for the first time and was taken over by financial institutions.
Other thing is up to personal taste, but I must admit I much prefer deck
layouts of old GibSeas (and old Bavarias) over old Moodys.
I met also few old Moodys in Eastern Med., they were in good condition also, but I can not tell that they aged better than GibSeas or Bavarias.
Good luck with Your search