Plone 4.3 + RelStorage + PostgreSQL: Postgres versions?

I have changed my Plone 4.3 setup to use RelStorage[postgresql]. Now this doesn't perform as well as it could because the database server is not (yet) separated in a dedicated server; I suppose, the most important part would be the database to use its own disk (preferably an SSD). That's not my main question, but remarks are welcome.

My main question is: Can I use the most current PostgreSQL version, or should I e.g. stick with 9.x (for now)?

Because of Plone 4.3, I currently use RelStorage v1.6.3 (and psycopg2 v2.5.5).
I'd need to update PostgreSQL anyway because PostgreSQL 9.3 has reached its End Of Life in November 2018.
The only information about version considerations I could find so far is that "RelStorage 2.1 performs best with PostgreSQL 9.5 or above".

Of course I plan to update to Plone 5.2 and RelStorage 2.1+ during this year, but I'm not yet ready to do so.

I'd give latest a go.
Try to see if there's a performance degradation somehow.

Thank you; zodbshootout looks interesting. This will help. To fully make use of it, I'll need a bigger playground than I currently have.

Regarding my main question (which you answered "I'd give latest a go"), I was hoping for answers along the lines of

We use Plone 4.3.x with RelStorage x.y and psycopg2 x.y, talking to PostgreSQL x.y, in production without any issues

Maybe @jensens can shed a bit of light on this?

For Plone 4.3.x use RelStorage 1.6 (latest). For Plone. 5.x use latest RelStorage (2.x). Postgres Version can be latest or IIRC any 9.x.