Recommendations on 3rd party software

In the documentation are at least two specific recommendations but not specific note why.
Would be nice to know why the choice is:
apache2 over nginx
postgress over mysql

Hello. We recomend to use Apache because sometimes we make changes in .htaccess. So customer will just upgrade the system and everything will work without additional configurations of webserver. We recommend postgres because it is faster and works better with large amount of data.