I'm not sure I could write a straight urban fantasy any more than I could write a straight contemporary story. I would end up being intimidated by all the small details.
I think predictability is built into any good novel in some way - you begin reading Anna Karenina and you know pretty much what's going to happen at the end. But that doesn't mean you know what's going to happen in the middle. For me, it's that sense of what happens in the middle that's important.