In my mind, MySQL no longer exists. It’s a weird Oracle thing that I wouldn’t touch with a lineman’s pole. MariaDB is what happened after MySQL disappeared.

I think it gained popularity over a decade ago, when it was faster because it was unsafe.

In the end postgres is the better one. With mysql the defaults are bad.

I wrote this in another comment, but it's relevant here I think:

" I do scaling and performance work, mostly with Rails apps, but a significant amount of the work is database level and not language specific. I've used both postgres and MySQL (and a few other databases) going back to 2000.

The best thing I can hear from a company when I start is "We use Postgres". If they're using postgres then I know there's likely a far smoother path to performance than with MySQL. It has better tooling, better features, better metadata. "

Right now I would not choose MySQL over Postgres at all, ever. I can't think of a single way it is materially better.