When comparing Postgres vs MySQL with InnoDB, the Slant community recommends Postgres for most people. In the question“What are the best ACID-compliant scalable databases?” Postgres is ranked 1st while MySQL with InnoDB is ranked 3rd. The most important reason people chose Postgres is:
Built by passionate developers, available for free, and is well supported by its active community.
Ranked in these QuestionsQuestion Ranking
Pros
Pro Open Source
Built by passionate developers, available for free, and is well supported by its active community.
Pro Supports migration from other major proprietary and open source databases
With the extensive SQL support and migration tools, Postgres users are easily able to migrate their databases over to the Postgres database with little effort.
Pro JSON support
JSON support allows for Postgres to transfer data as raw text and without attributes and markup overhead. This will result in new levels of speed, efficiency and flexibility for developers.
Pro Highly scalable
Continues to work well under low or heavy loads in order to meet the users' need.
Pro Object-Oriented Database
You can reuse existing approved design table and extend its capability by inheritance. You can reuse ancestor method byy declaring new trigger for descendant but reuse ancestor trigger procedure. You can add, remove or override column constraint making it differ from its ancestor. Applying OOP with database design help me reuse, extend, and encapsulate business logic and end up a rapid design, and less errants. PostgreSQL is a powerful RDBMS while its OOP is sufficient for OOP modular design. Especially its Open Source ,and free.
Pro True ACID-compliance
Built in, so users won't have to worry about atomicity, consistency, isolation and the durability of the database.
Pro Multi-Version Concurrency Control (MVCC)
Postgres uses MVCC. For each user connected to the database the Postgres database shows a snapshot of the database at a particular instance. When the database needs to update an item it will add the newer version and mark the old version as obsolete. This allows the database to save overhead but requires a regulated sweep to delete the old, obsolete data.
Pro Multiple Language Interfaces
"There are interfaces for Java (JDBC), ODBC, Perl, Python, Ruby, C, C++, PHP, Lisp, Scheme, and Qt just to name a few."
Pro Great query planner
Unlike MySQL, you generally don't spend time on hinting the query planner in order to make PostGres perform well.
Pro RETURNING option on INSERT queries
For example:
INSERT INTO table (field_1, field_2, field_3) VALUES (value_1, value_2, value_3) RETURNING id;
Pro Multiple APIs
Some of these APIs include ODBC, Java (JDBC), Perl, Python, PHP, Ruby, and native C. Also, there are a number of third party APIs that are available for use to interact with the database
Pro Many applications available
There are a number of applications that are built with the focus of MySQL. Some of these include Drupal, Joomla, Wordpress and more.
Pro Scalable
Works well under simple operations or heavy tasks.
Pro Huge community support
Being the world's most popular open source database means there are tons of available examples and information for users' to access.
Cons
Con Overkill for simple setups
If a database will be doing many simple operations Postgres may be over-kill.
Con Vaccuuming can cause headaches

Con Can't be run as an embedded database
Con InnoDB is not fully configured
When you initially install MySQL, InnoDB needs to be configured to make it suite your needs and there are many issues you can come across.
Con Highly dependent on hard disk performance
