One difference that I've noticed between writing out and out comedy and what I must laughingly call 'serious' urban fantasy is the extent to which it's acceptable to get off the point. Obviously, everything should contribute something, but in serious writing that becomes an imperative to cut every word that isn't catapulting things forward. With the comic stuff, there's slightly more scope for digression, so long as it connects to the main point. As an example, yesterday I got to write an extended bit about urban wasteland as a lead in to the arrival of a group of characters. It's the sort of thing that I would have cut immediately from either of the serious books, but which is absolutely perfect for what I'm working on now.
The best bit, of course, is that if you plan it properly beforehand, even the weirdest excursions end up adding to the overall piece, because the plan ensures that everything you're building the funny stuff around is an essential piece of the plot.