Ask this questions yourself? And you will decide your DB selection.
- Do you need master-master? Then CouchDB. Mainly CouchDB supports master-master replication which anticipates nodes being disconnected for long periods of time. MongoDB would not do well in that environment.
- Do you need MAXIMUM R/W throughput? Then MongoDB
- Do you need ultimate single-server durability because you are only going to have a single DB server? Then CouchDB.
- Are you storing a MASSIVE data set that needs sharding while maintaining insane throughput? Then MongoDB.
- Do you need strong consistency of data? Then MongoDB.
- Do you need high availability of database? Then CouchDB.
- Are you hoping multi databases and multi tables/ collections? Then MongoDB
- You have a mobile app offline users and want to sync their activity data to a server? Then you need CouchDB.
- Do you need large variety of querying engine? Then MongoDB
- Do you need large community to be using DB? Then MongoDB