WHMCS vs. Pro Sites?

I am wondering what plugin/business model to shoose from… My company basically does what edublogs does. I want to have a free level with no obligation to upgrade, a pro level where user gets more functions in my MU-enviroment, maybe a hosted WP level geared toward professional personal bloggers, and a campus level wher ewe add all good stuff readyto run out of the box.

WHMCS is something I just nowstumbled upon, and its why I ask this – what does WHMCS offers, and is that even comparable to Pro Sites? Which one should I look at in my case?