Depends rather on your own abilities and preferences.
Ask yourself:
1. Can you make a reasonable assessment of the condition of the boat you are looking at?
2. Are you generally handy, confident of your ability to carry out elementary carpentry, plumbing and electrical works (leaving the really technical stuff to professionals where appropriate)?
If the answer to both is yes, go to it.
Over the 7 years since we bought our now 100 year old tjalk Anna Maria in 2007, most of those boats we have met which have had recurring problems have in fact been new-builds (mostly UK built)!
Raised on an Australian farm, now a retired consulting engineer, and a repeat renovator of the succession of old homes I have lived in, the answer (for me) was firmly buy a tried and proved old boat, but make sure you view and assess plenty of boats before you make a choice.
In our first full summer of ownership (2008) we sailed nowhere. In the gaps between my trips to Singapore for a project I was completing, we grew to know the layout of Anna Maria intimately. This period confirmed my assessment that she was inherently sound and well maintained, but in some ways dated - no generator and electrical power-management system, insufficient water tankage, 1968 boat-style "bathroom". The previous owners had, over 35 years of ownership, maintained her well, but had used her mainly for weekend and short holiday voyages.
In this period we renovated the interior fit-out (mostly re-using the lovely existing materials - difficult to do with a contract to a tradesman), turned one cabin into a proper bathroom (with washing machine etc) and over the ensuing winter (2008/9) had the workshop of our marina (where Anna Maria had lived for the past 20 years) fit the essential generator, Victron system, extra water tanks etc, ready for our Springtime return to the Northern Hemisphere.
Over each of the subsequent years we have travelled about 2500km.
2009 - Friesland to Paris and return (AM wintered in Friesland)
2010 - Berlin and Mecklenberg and return (AM wintered in Friesland)
2011 - Strasbourg, the German and French Mosel/Moselle including Cochem and Luxembourg, and then down to the Saône (AM wintered in St Symphorien)
2012 - Burgundy to Paris via Pouilly tunnel, back to Dijon via Loire, Nivernais, etc, (We wintered on AM in Paris Arsenal)
2013 - Paris to Harlingen NL (for our 7-year survey and for TRIWV certification) and return (We again wintered on AM in Paris Arsenal.
2014 - Paris to Flanders - where we are now (we will leave AM in Friesland this winter while we co home for a proper southern Summer).
So after the initial year we have enjoyed nearly 6 years and 15,000km cruising in 5 European countries, without a single significant ship-related problem. Obviously the hands-on approach to renovation has paid off - I know where every cable and every fitting is, what it does, and its condition - a great confidence booster when cruising somewhere remote or where my language skills are overstretched!
My advice - If you like old ships (and houses, as I do), and if you feel you can do it, buy a tried and tested "oldie" - (as we ourselves are!).
However if you are not confident (and can afford the extroardinary elevated prices asked for new ships or for "professional" renovation, good or bad) that is what you should do.
Charles Fitzhardinge
Anna Maria