I have only had one new car; the 1999 Jeep Cherokee I have today.
My first car was my mon’s 1966 MGB roadster. It didn’t run when I got it, and needed an overhaul to get it on the road. A front axle broke once. It seemed to have a propensity to develop oil leaks. The springs were worn, and it tended to drag the exhaust pipe over speed bumps. The (new) hood did not fit well, so I’d get wet occasionally; especially if someone hit a puddle beside me. The windscreen leaked and I’d have to wear a garbage bag over my left leg to keep it dry during the monsoon months. My next two cars, owned concurrently with the '66, were 1977 MGBs. They liked having electrical problems. For example, one had a fan that would turn itself on for no apparent reason (even when the engine was cold) and run down the battery. The hoods fit better and I could stay dry, but their rear windows (as happens with convertible hoods) were yellow and cloudy. (Fortunately, they zipped down so I could see in the good weather that prevailed in my area. Usually two of the three cars were running at any given time.
I replaced the MGBs with a 1977-1/2 Porsche 924. An excellent little car unfairly stigmatized because of its mixed heritage. Still, it had problems. There was a strong smell of fuel when the tank was filled. Mechanics never could find a leak. The windscreen wipers would turn on in hot weather for no apparent reason. I had to pull the fuse, and then replace it when it rained. The transmission needed to be rebuilt soon after I got it. I replaced the engine at 140,000 miles.
My next car was a 1988 Chevy Sprint Metro that I got with 12,000 miles on the clock. No problems with that one until I crashed it. The next car was a 1985 Sprint (not Metro). It also worked well, but having more miles on it it did not last long. I decided I had to get rid of it when there was a small engine fire.
Next came a 1979 Porsche 911SC. This car was the most fun one I’ve had. Its aging suspension needed to be replaced (I had a race shop put in some nice Bilstein sport shocks). The steering failed one day. I made a right turn and it froze. I was able to get it working through brute force, but the steering mechanism needed to be replaced. I had to replace the timing chains and tensioners. Every time I took it to the shop it cost about $400.
I had a 1979 Honda CX500 motorcycle (after having had two new Yamahas). It had a problem with the thermostat and would overheat. I lost first gear fairly early on. (But it worked okay starting from second.) Hey, I bought it for a dollar. But I got my next bike new.
The Cherokee (which replaced the 911) has been relatively trouble-free. I lost one computer module, but it was covered under the warranty. The “neutral sensor” failed, and that too was repaired under the warranty. The vent switch failed twice, and was repaired under the warranty.
I’ve always had problems with used cars. The problems I’ve had with the Cherokee and the Yamaha were taken care of by the warranties. Given that, I’d tend to buy a new car instead of a used one. This goes for my primary vehicle. I’d have no problem buying used for a second car, but I like having a car whose entire history I have experienced.
On the other hand, some cars hold up better than others. MGBs are notorious for their maintenance requirements. Sprints are so cheap as to be virtually disposable. Porsches are great cars, but repairs are expensive and older ones usually need work. If I needed a boring commuter car that is reliable, I’d have no problem getting a used Honda with 30,000 - 40,000 miles on it.