Possibly an overly simplistic comparison given then number of engines available for MySQL. Have a look at http://www.wikivs.com/wiki/MySQL_vs_PostgreSQL for some comparison
In my personal experience, Postgres is much more scalable and has much deeper level of optimization that can be done by the developers. It also provides a lot of features that MySQL simply doesn't have - Arrays, custom aggregation functions, interval datatypes, advanced datetime function, its 'programming' language (PL/PgSQL) is amazing, better trigger handling, and much more.
Granted, PostgreSQL does contain more features, but I still think mySQL is a better choice for 99.5% of online operations out there.
PostgreSQL is better and feature rich than MySQL. Especially, if you want some spatial data manipulation you can use the powerfull postgres extension postGIS
PostgreSQL is better for some types of web-services, but MySQL is faster for read-operation and for the most websites.
it all depends on what you are using it for? there is many factor in comparison but over all PostgresSQL is much much better both with optimization option and also for performance with procedure language there is many features that postgress have but not mySQL
You can use MariaDB which is a fork of MySql [Practically The Same] which is definitely better that PostgreSql.