Few years back I've had friend explain the difference between MySQL and PostgreSQL like this:
- MySQL: do it fast, then make it right - PSQL: do it right, then make it fast
I had switched after learning that CHECK constraints were parsed, but ignored -- I've yet to be as offended by a program that at that instant
Apparently supported now but what the hell; I don't think they even threw a warning about it
Years back, the conventional wisdom seemed to be that MySQL used to be faster, and PostgreSQL more correct. Over time, according to that same conventional wisdom, MySQL got more correct than it used to be and PostgreSQL got faster than it used to be.
Overall, my impression is that the project's philosophy is to do the Correct Thing, even if it's slow.