Couchbase and Neo4j are both distributed databases with vector search capabilities added on, but they differ in their core technology and use cases. Couchbase is a NoSQL document-oriented database that can store vector embeddings within JSON documents for similarity searches. It offers flexibility in data modeling and integrates well with external tools and frameworks. Neo4j is a graph database that combines graph relationships with vector embeddings, allowing for seamless integration of vector search and graph queries. It's suitable for applications requiring both graph structures and high-dimensional vector data. The choice between Couchbase and Neo4j depends on the specific use case, type of data being stored, and performance or integration requirements.