Last I looked, foreign key constraints didn't work. This seems to be fixed now innodb, but requires migration to innodb.
Last I used Postgres it had a nasty memory leak that crashed the production DB at work at least once a day. I believe it was fixed several years ago though, which I also believe was a couple of years after InnoDB and foreign keys made it into MySQL, so I don't go around telling people that Postgres leaks. :)
I agree that many of the MySQL defaults are annoying and end up as hard lessons sometimes, but I also agree with dragonchild that DB administration is not easy and without reading the documents thoroughly bad things are likely to happen with just about any software.