When comparing Redis vs CouchDB, the Slant community recommends Redis for most people. In the question“What are the best NoSQL databases for web applications?” Redis is ranked 2nd while CouchDB is ranked 3rd. The most important reason people chose Redis is:
Redis has [great docs](http://redis.io/documentation), an active mailing list, and a github community.
Ranked in these QuestionsQuestion Ranking
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 Redis is written in ANSI C and therefore doesn't have a VM
Pro Works well between physical network partitions
CouchDB works very well even when the network is physically partitioned
CouchDB is considered an available DMS according to the ACP theory of database management. As such it allows every client to always read and write
Pro Useful for applications where versioning is important
CouchDB is mostly used in applications where a large amount of data needs to be accumulated and where data only changes rarely.
Pro Changes API
You can use the RESTful API to listen for changes in your database, which is something most databases can't do. It makes it really easy for clients to keep their view of data up-to-date.
Pro RESTful API
Con Can only achieve consistency through replication and verification
Since CouchDB is considered an AP (Available, Partition-Tolerant database management system), it is not really consistent (not all clients can have the same view of the data consistently) and the only way to achieve some "eventual consistency" is through replication and verification of data.
Con Uncertain future
After a very promising start, development began to drag after major supporters like Canonical, Selenium and CouchOne either shut down or moved to other tools. Development has begun to pick up again.