I have always preferred PostgreSQL over MySQL - but, I usually end up using MySQL because it is installed and configured on servers and virtual servers that I rent on a monthly basis for my customers' and my web portals.
MySQL Corporation's contract with InnoDB's owners is up next year, but Oracle plans to renew some agreement - it will be interesting to see how the use of MySQL in non-commercial licensed environments holds up.
I am thinking, but have not made a firm decision, of switching over to PostgreSQL for all deployments. This will add to the (now small) overhead for renting a server and deploying a web application. I might also start to favor hosting companies who provide pre-installed PostgreSQL.