So it may surprise you that I'd recommend taking the Google offer! In my mind, there's no way to lose choosing Google. If it turns out that you love Google, awesome – you can have a great and well-compensated career there. And if it turns out you don't enjoy that kind of shop (like me), your career possibilities will be far wider after a tour of duty at Google than they are right now, including within startups. Google as a resume item will continue paying dividends for as long as it maintains its reputation for engineering excellence.
This advice is based on my personal experience – it's almost certain that I wouldn't be in my current role if I hadn't had Google on my resume when I applied. And my current responsibilities, experience and income far exceed what I could have expected on the alternative trajectory at an early-stage startup, unless its growth happened to have exploded while I was there.