Hi and welcome to the Forum!
VPN's are very useful for security reasons when accessing free public wifi or accessing certain subscription services when not in the country of use. Also great for accessing Facebook where this is not available eg China.
As far as the Prism angle is concerned, my thoughts are that if our Governments want to spy on us, then nothing will stop them.
But then you may already know all this seeing as you appear to already have a VPN service. Is it not good enough?
Hopefully our members will be able to assist you. Enjoy!