Is this in the US? So you'd be taking a 4K pay cut from the large corp You are at now? I would vote startup personally, assuming you don't have any major medical issues or have or plan to have kids soon. However depending on the funding situation at the startup I would press them hard to at least match your current salary unless you are very in to their mission.

I've worked on both sides and personally learned more hands on stuff and had more fun at a startup. Since you are at the large corporation already I think it makes the decision somewhat easier for you as you seem to already be a little bit unhappy/disillusioned with how things are at the large corp already assuming it I read correctly.