What determines this stat? I'll use one spell for hours, then use another spell for five minutes, only to have the five minutes spell listed as my favorite in my stats. It seems like it's more of a "What you've used recently" stat than an actual "favorite" stat. Currently, it lists my favorite as Arniel's Convection and I only used that for a few seconds in a quest...

Oh I thought this was another one of those "What's you favorite weapon" threads.

I don't really know what determines what you're favorite spell is. You would think it considers the most used spell as your "favorite". On my game it lists Summon Dremora Lord as my favorite, which is about right. I've casted that spell so many times because it only lasts 60 seconds. Dumb game doesn't have a spell to permanently summon a Dremora.