An On-site installation of ALM-PC 11.52 X should meet all your testing need. To test your Cloud base application, you need Access to the Application from:

1. The computer(s) with VuGen installed to create scripts.
2. The PC hosts and Load generator(s) must be able to access the application just as if a real user would from the machine, in order to run the load tests

The next thing is having the correct license bundle(s) for the protocol use to script against the Application.

The ''Performance center on SaaS'' is an option from HP to ''rent'' ALM-PC and works the same as on-site ALM-PC the big thing is they or a partner maintain the ALM-PC system.

Performance center on SaaS ''is On-demand performance testing. Built on HP Performance Center, this on-demand SaaS solution enables you to load-test applications in and from the cloud. You can purchase the number of virtual users and protocol types you need for as long as you need them and scale up or down as projects evolve. Performance tests can be executed from load generators in the cloud or on your premises behind a firewall. And you can leverage the solution to build an entire practice and center of excellence to govern application performance across your enterprise.