PostgreSQL 9.6 is now out! Here is the official announcement for this latest version of the PostgreSQL database. I’m very excited for this release now that parallel queries are supported.
For the MAC URISA 2016 workshop (to be held on October 12, 2016) I have stated that the preferred version is (at least) 9.4. ESRI has stated that ArcGIS support is limited to 9.4, which is why I ask attendees to install at least version 9.4.
In my experience using ArcGIS with PostgreSQL, the support has gotten better and considerably more stable over the years. While I haven’t tested every permutation of ArcGIS, PostgreSQL and PostGIS, you should be safe to use the various components together, as long as you are close to the “official” version. Of course, stick to what is recommended if you are using PostgreSQL in production, especially if you may need support from ESRI.
Naturally, if you are not tied to the ESRI stack, you are more free to choose the PostgreSQL version you would like to use. While I’ve not yet upgraded to PostgreSQL 9.6, I am looking to do so by the end of the calendar year.