All else being equal, considering the reliability of instruments, human factors, etc., is it safer to fly in a piston-single GA airplane with steam gauges or with a glass cockpit?
In other words, if I want to buy an airplane (hypothetical; I'm definitely not buying an airplane any time soon) and I see two planes that are identical except for the avionics, and safety is the only factor I'm considering in my decision, should I buy the one with a glass cockpit or with steam gauges?
With rare exceptions, such as a retired fighter pilot or an ATP leisure flying in their spare time, the weakest link in a GA aircraft is overwhelmingly the pilot.
Most accidents are straight pilot error, followed by engine failure, and it's the lack of flight recorders that keeps us from learning what caused the "unknown" accidents.
Whichever display is easier for you to understand is going to be safer. Even non-certified avionics' failure rates are small compared to pilot failure in reading them.
Everything else equal, such as when learning from scratch, glass cockpits make it easier to avoid trouble. They offer GPS navigation, which is hard to misread, can display maps and traffic information, are easier to read, and sometimes include automated warnings.
That said, for pilots who already have a lifetime's experience of reading traditional gauges, it can be worth more in an emergency than the convenience of digital readouts. High stress can cause mental regression, reverting to the earliest memories of similar situations, and first training with steam gauges will transfer well to any aircraft that has them.
P.S. Technical addendum:
As far back as 1949-1953, there was a series of studies, the first involving 97 military pilots, which proved digital and single-hand dials to perform well, but dials with 2+ hands, required for e.g. altimeters, an ergonomic challenge. This has led to an increase in the use of digital counters, back then mechanical. Moving tape was deemed the best (the last design, "I", doesn't show the value's rate of change).
Glass cockpits offer a total solution. But they place a lot of information on one screen and expect the pilot to know where to look for what, how to change modes when needed, and what each mode entails. So training and regular practice with the specific PFD (primary flight display) layout used are essential to keep their reading intuitive and automatic.
Figuring out an unfamiliar PFD can take a lot of time the pilot might not have. Steam gauges aren't great, but they share a mostly-consistent design across every aircraft that has them as primary instruments.
