To have a look at what's new in 9.6 see:
https://wiki.postgresql.org/wiki/Newin96Quick list of major features:
Parallel sequential scans, joins and aggregates
Elimination of repetitive scanning of old data by autovacuum
Synchronous replication now allows multiple standby servers for increased reliability
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Support for remote joins, sorts, and updates in postgres_fdw
Substantial performance improvements, especially in the area of improving scalability on many-CPU servers
