Currently, there are two SDN releases:
Spring Data Neo4j 3.4.0.RELEASE
Spring Data Neo4j 4.0.0.RELEASE
What is the point to have them both?
Which one should I use in my application ?
Spring Data Neo4j 4 is the newest version, a complete rewrite from scratch focussing on Neo4j server, see also:
http://neo4j.com/developer/spring-data-neo4j/
It builds on top of a pure Java OGM which uses the server transport and will use the binary protocol in the future.
There are migration notes for people coming from SDN 3
If you are starting a new project go with SDN4