During the early 90s GURPS Mage the Acension came along with GURPS Voodoo. Both had radically different magic system yet still worked within GURPS.
GURPS Mage was definitely the most powerful system. I tweak to make it the type of magic the Gods used. The mana system that clerics and mages used was a pale shadow of what is form of magic could do.
One thing I had to change was what Paradox was. In the normal Mage game Paradox occured whenever a normal person saw something that couldn't be done by science. It represents the dominant reality of reason punishing the mage for defying it.
For the Majestic Wilderlands I decided that Paradox occurred when creation was bent in unnatural ways. The world was created from chaos using natural laws. Mana is a force that can be manipulated by will. A force that was created alongside the other natural laws. Mage Magic in contrast is the very bending of reality itself. Defy the natural laws then Paradox kicked in.
One thing that prompted this post is that I am sorting all my gaming stuff after cleaning the garage. I have a dozen White Wolf books including all five of the original World of Darkness Games. I wondered why the heck I bought them. I despised the tone of the campaign they had and the mechanics were blah. Then Tim's post at Gothridge Manor reminded me.
They make some of the best damn monster manuals ever.
Excuse me as I hang garlic and load up on silver bullets. I think I hear the howling of White Wolf fans.