CentOS - Apr 2018 - Centos 7 LAPP setup Postgresql version and setup

Hi all,

I've got a nice shiny new server which I'm going to build as a LAPP
platform.

I've just had a quick look for suitable instructions on the best way to 
configure it and I have a few questions. There are many hits, some better 
than others.

(It is replacing a Fedora 9 server so I'm expecting to have lots of *fun*)

1) 9.2 vs 9.5

Some of the instruction pages I've found install using the standard 
repositories and install version 9.2 (?) while some others add a postgresql 
repo and install 9.5

What are people's opinions? In the long term, and I going to have more admin
hassle with one over the other? 

Will porting schemas including stored functions in pl/psql from 8.3 be 
easier / better with one version over the other?

2) network vs sockets 

I read somewhere that connecting Apache / PHP to Postgresql is faster if you 
use sockets rather than usling the loopback i/f.  Is this correct? If it is 
correct, what is the correct connect string if I use the 9.2 or 9.5 RPM's as
described above?

There seems to be lots of Google content about sockets not working. Is it 
really that hard?

(I use pg_pconnect() to do the connecting)