Couchbase and Apache Cassandra are both distributed NoSQL databases with vector search capabilities as an add-on. Couchbase is a flexible option that allows developers to implement custom vector search solutions, while Cassandra provides integrated vector search capabilities through its Storage-Attached Indexes (SAI) feature. The choice between the two depends on specific project requirements and team expertise. Couchbase is more suitable for projects that require a flexible NoSQL database with customizable vector search solutions, whereas Apache Cassandra is better suited for large-scale, distributed applications that demand native vector search functionality.