The number one rule — and I cannot emphasize this enough — is that you should not work at a startup for the money. The risk adjusted returns are not terrible if you know how to screen for good founders. It is, however, exceedingly unlikely that you make more than $10m over ten years — especially considering investment returns on your comp today over that time period.
So it depends on what you want.
Startups offer flexibility, opportunity to shape a company and its culture, building a team, incredibly fast growth (both personal and company), and the opportunity to touch many-if-not-all parts of the company.
The downsides are lower comp, longer hours (if you’re actually going to see returns), less support. For engineering, for example, big company employees drastically underestimate how much they rely on homegrown tooling.
Whether that’s worth it to you isn’t something I can answer. You will make less money. Probably a lot less. There are things you get that might be worth more than money, especially when you already have a lot. But also maybe they’re not to you and that’s okay!