There was no version 13 of SEP

Symantec decided to skip it (I guess it was bad luck)
I am currently using SEP 14 (unmanaged client) and I am happy with it. I has one of the bes IPS for enterprise endpoint and I hope that with the acquisition of Bluecoat the product will be much better (share Databases etc). Having said that , messagelabs was a great product until Symantec acquired it and became symantec cloud

AML technology is catching up and it is a great improvement of sonar
It depends what you are looking for though?If you want to compare v 14 with 12 then yes, it is a great improvement. I am not going to debate which AV solution is the best cause they all have their own issue/bugs/CVE so whatever solution you go with, always keep in mind to have a "defense in depth " model
What's new in Symantec Endpoint Protection 14