If you're not $60-80k sure that you want a 12c then buy a used one. If you are 100% sure you want one, and will keep it for more than 15 minutes (you are not the guy keeping up with the Jones' and change cars like you change shirts) then buy new - you get exactly what you want in the color you want. You will also be a "new buyer" vs a "used" buyer/vulture in the eyes of the dealer (applies to any dealer).
FWIW I bought my 12c use, when the 12c was introduced I was too blinded by HP numbers and magazine reviews that I never considered it. A year and a half later I contacted the dealer, a track day later I immediately saw the error of my ways. Then I found the intangibles of the early car I really liked (swipe, built in MTC) which put me in what seemed like an undesirable VIN range...great! More for me as the saying goes! The only thing I wish could be retrofitted is the lift system, but I'll take the swipe over the lift. To each their own.
Another consideration is what I told the dealer in the process of buying my GT Speed "I'm not willing to take a quarter million dollar chance to figure out if I like the car/brand or not. If I buy used and decide I don't like the car I can get out with a sunburn, not 3rd degree burns and skin grafts." To that point My first Aston was used, my 2nd was new & I got exactly what I wanted. An new Aston is not a sound financial decision, neither is any new exotic. Obviously enough folks get it and they continue to sell thousands of new ones every year. People do many things in life that are not sound financial decisions, Vegas, vacation, cable TV, etc. Making decisions based upon your CPA's advice leads to a very boring life, but you'll die loaded.
All the "differences" that make newer cars better I found disliking. The ugly rubber button that you can see standing outside the car (installed because of negative press reviews/magazine morons) - Dennis had enough so here's your freaking button. The only time it's difficult to open is when it's humid outside and your hand skips instead of gliding, messes up the motion. Works great when wet because your hand glides. Early cars were built in the MTC next to the F1 cars - means jack crap to everyone else but I sure apperciate it. They were also much more hand built with less jigs and such...sure the fit and finish is less than new ones but it's a mark of the small size and human touch that high volume production cars have Q/A'd out. Look at an old Ferrari, Aston, etc. not a straight screw head or stitched seam anywhere in the car - the imperfections are the sign of hand built 1 at a time cars. I still struggle with how perfect a Bentley interior is....then finally I found a wave in a seam....great, it IS hand built.
It's called character IMO. If folks want perfect buy a Lexus where several people operate machines that stamp out perfect copies that are flawless and ensure you car is exactly the same as the other million they sold that year.
I think about building from scratch projects with my kids. We spend a lot of time making them perfect only to find in the end they are far from perfect. I figure cars like Mercedes, BMW, Lexus, Infinity, Porsche, Corvette for folks who want flawless high production paint and interiors. What used to be a badge of honor (hand built) is now becoming a dirty word... For $300k you'd think they could paint a car.... The other extreme would be to buy a Vette and say for $100k you would think they could cover the whole seat in leather, not just the seated surface. Luckily MSO exists. You can have perfect everything, completely bespoke and spend $500k+ for a car worth $250k the minute you title it....
Soapbox aside, McLaren will go to every length to fix a quality or workmanship defect, that is what's most important. So when you walk into your garage to find your windshield cracked from top to bottom right down the middle they will say, yep, problem on early cars, when would you like us to pick it up and replace the windshield (under warranty at no cost).
Personally I don't get the big deal with the paint, no one notices at a car show and unless it's peeling off the rear bumper GM style, no one is going to notice when you're driving. It could be peeling off the front bumper and only the Aventador drivers will notice.