I have seen nothing to indicate the Mac mini has been changed so yes it is still the 2014 model. As a server what do you want it to do? File server, email server, VPN server, media server, etc.?.If so, do you need them both to perform as servers or just one?.It will really depend on a number of things: I was adviced to go for the model with the default 1TB 5400rpm HDD, buy the upgrade to the 3.0Ghz i7 and then replace that HDD with the SSD from my current Mac Mini. If it is, I want to replace the HDD with an SSD (Samsung EVO 850). I still use the 2011 mini as a file and media server and it currently is running OS X El Capitan Server.

I do not have the Mid 2011 mini Server, but do have both a Mid 2011 non-server mini and a Late 2014 mini and I can attest a significant performance improvement with the newer model overall. You can compare it against the 2011 version (there is no Late 2011 model however, there was a Mid 2011 mini Server) using Apple Support - Specifications.

The latest (currently) Mac mini is a Late 2014 model. I'm thinking of replacing my late 2011 Mac Mini Server 2GHz i7 with the latest 3Ghz i7 model from 2017.

2017 mac mini