Personally I'd go with IPsec since I'm familiar with it, but it really shouldn't matter.
All you'll want is to make sure that the VPN appears as an addressed interface on both ends, then set up the VPS to do NAT with the VPN interface being the "inside". Configure pfSense with the proper rules so the box you're using is routed over the VPN and you should be good.
I don't have my pfSense box hooked up right now (running an 1841 so I can learn IOS) otherwise I'd try it with my dedicated server and post specifics, but maybe someone else can fill in the blanks.