1. What exactly do you mean by "a storytelling game?"
2. Also: A god trying to kill you will probably take about 90 seconds. A 20-shift evocation takes little time to resolve. No need to worry about wasting time.
3. Also: Nobody can improvise infinitely well. The argument that you should be able to improvise would also justify not making a city or any NPCs at all. In fact, it would justify that better. The weaker the NPC, the easier it is to make (generally speaking).
1. Any story that the player has more say in what is going on or that has a more social setting. D&D can be very social, but hte GM has total control (in most games) and can be nothing mroe than dungeon crawls. White Wolf systems and DFRPG seems to be more about the story than the loot and dungeons.
2. You under estimate how twinked out a character can get in a short time. I will admit - 2 hours was hyperbole. The fact that combats even against superior oposition can become protracted and slow the game to a crawl where most other players are sitting with their thumbs up their collective rears is what I was reffering to. Statting something makes it possible.
3. I think you may be taking my opinion of improvising off the deep end. True enough a plan is required but not being able to improvise at all is a bad idea.
If your game is in... Texas and the PC's want to go to Mexico and then further south to mess with red court leaders, you'll likely need to improvise since this idea seemingly came out of left field. You may not have the nobility statted to perfection. They deserve more than a template in a book. What do you do, some GM's can't deal with that. I think all Gm's should be able to.
I'm not saying Richard_Chilton agreed or disagreed with me: however, as you can see - sometimes statting a god can be detrimental to a game. Set got stomped flat. Once that happens by the way. Once a veritable god is defeated, many players (or at the very least characters) will become very jaded to danger. They get big egos. Well deserved big egos in my opinion. Then you have two choices.
1. Prove them wrong - crush their egos and establish other things are meaner than gods and meaner than god slayers
or
2. Deal with the fact that your villains and antagonisits no longer scare/intimidate them.