That isn't unique to pg though: just look at the number of performance questions in dba.stackexchange and on web hosting forums that, once you take out those that turn out to be bad queries and/or non-existent/inappropriate indexes, come down to tuning certain settings in my.ini.
I've not used either for a long time so my knowledge may be out of date, but mysql definitely used to be the easiest to get started out of the box which was part of the reason it won out in the shared hosting space. Of course the main reason it won out in that area was because it was faster than pg in many artificial benchmarks because at the time it didn't bother with silly things like transactions (as MyISAM was the default table type), and foreign key constraints, and other necessities…
I've not used either for a long time so my knowledge may be out of date, but mysql definitely used to be the easiest to get started out of the box which was part of the reason it won out in the shared hosting space. Of course the main reason it won out in that area was because it was faster than pg in many artificial benchmarks because at the time it didn't bother with silly things like transactions (as MyISAM was the default table type), and foreign key constraints, and other necessities…