Having said that ... your chance at working on an interesting project is higher at a startup if you are the kind of person that can land a spot at Google/Facebook. What I mean is, you'll be a big fish in a small pond. The kind of person that gets buried in some obscure ad-tech team at Google, for example, can pick and choose the projects he works on if he shops around at a lot of startups. Want to work on an open source database? I bet you can find a place that will pay you 100K to do that ... but your stock might be worth nothing in four years ... and if you worked at Google your compensation would be around 160 and your stock would be worth around 750K.
So you really genuinely have to love what you do. And if you want a family you have to be prepared to move out of the Bay Area when you fail ... because you won't have enough money to buy a house the way your peers at Google and Facebook will.
So being at a startup you need to make peace with a lot of very probable outcomes ... moving away from California, possibly starting a family later, etc.
On the positive side, you can choose the area of technology you want to work on. And if you chose well, there's a chance you can parlay that for future returns.
I haven't even touched on the role of purpose and lifestyle ... mainly because I think its simplistic to assume a startup will give you purpose and a big company won't. I think purpose is something you'll have to shop for ... just like you shop for the right project.