Re: MySQL versus PostgreSQL comparison
In the early 2000s MySQL's marketing was better and this helped push the LAMP monstrosity and its related bad practices onto a grateful world.
MySQL was a company that understood the importance of getting on PFY's notebooks, which were mostly running Windows and so they provided a Windows installer. Postgres had to be installed using cygwin: this worked fine but wasn't like to win any friends.
This helped favour MySQL and and encouraged development of PHP/MySQL stacks (with some fucking awful code most of the time). Database speed didn't tend to matter as it would be shot in the foot by the lack of connection pooling within a single page, let alone across sessions. And, oh yeah, there was the whole "parametrised queries, we've heard of them" versus "magic quotes" stuff. Magic quotes still make me want to cry.
I did some performance tests on something I was working on at the time and found no significant read performance advantages with MySQL. But it was faster for inserts – look ma! no triggers – as long as you could live with table-locking. Performance went down the toilet with joins; and a developer's life got harder because it meant manually adding indexes for foreign keys that Postgres ensured you got automatically.