Ars Magica, or some variation thereof

The appeal Ars Magica held for me was the idea that study and discipline of belief resulted in tangible power, and the balance between the inflexibility and compromises that behavior requires against the power it rewards.

To some extent these are the themes of WFRP, but I'd kind of like to run a game according to the book for once, if just to spare me the mental difficulty of tracking all the shit I've made up off-the-cuff. Also, the troupe-style of roleplaying, with a more episodic nature, might prove advantageous given our fluctuating group composition.