[Warm]

Saruman was making rings of his own. Of course I do not know what goes into making a ring (one day....) but I know that Sauron imbued his ring with a greater part of his own power. Before I would say that Saruman lost his power to his ring, I would think that the original ring makers wouldn't sacrifice their own power for a ring for someone else, would they? So, on one hand a ring requires power and on the other, no? Of course, this may have little to do with Saruman being able to defend himself, besides, he was still wearing the ring.

Clearly each wizard had different powers, as all Maia do. It had a lot to do with their teachers probably. Saruman was a student of Aule, just as Sauron. Gandalf was a student of Nienna and Manwe and Varda. I'm not quite sure where Gandalf learned fire, but lightning would come from Manwe I think.

What is clear is that Saruman could trap powers just as Gandalf suggested he might try with the nazgul, as he did with Gandalf himself, but as far as brute power, being a pupil of a craftsman, he probably didn't have much in any form. (Don't forget Sauron also had Melkor as a teacher)
Sorry for typos, still trying to get used to this nexus 7