When comparing Redis vs MariaDB, the Slant community recommends MariaDB for most people. In the question“What is the best database for backend web development?” MariaDB is ranked 1st while Redis is ranked 3rd. The most important reason people chose MariaDB is:
All development decisions for MariaDB can be reviewed and debated on a public mailing list or in the public bug tracker. Contributing to MariaDB is easy and the patch flow is fully transparent and public. But it's not all about the code contribution either - MariaDB also has very active documentation efforts and other related things that help developers in their day-to-day database administration.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Redis is written in ANSI C and therefore doesn't have a VM
Pro Good support
Redis has great docs, an active mailing list, and a github community.
Pro Redis uses the BSD license
This means that it is able to be used in a commercial product if one wants.
Pro There are numerous client libraries and frameworks to make redis more powerful
For Node.JS for example you can get something similar to what Parse.com was offering by using Node ORM.
Pro Truly open development community
All development decisions for MariaDB can be reviewed and debated on a public mailing list or in the public bug tracker. Contributing to MariaDB is easy and the patch flow is fully transparent and public. But it's not all about the code contribution either - MariaDB also has very active documentation efforts and other related things that help developers in their day-to-day database administration.

Pro More cutting edge features
e.g. GIS since 5.3
Pro Dynamic column support
MariaDB has dynamic column support which allows for some NoSQL type functionality. So one database interface can provide both SQL and NoSQL for different software development needs.
Cons
