I think the Occam's razor perspective here is that an engineering job at most of these companies is 90% the same, same-ish pay, same-ish equity, sort of mission

I think the Occam's razor perspective here is that an engineering job at most of these companies is 90% the same, same-ish pay, same-ish equity, sort of mission-driven-but-not-really work, etc. What breaks a company out of commoditization is often culture and so companies will go to great length to demonstrate their differentiator. (as a former founder and hiring manager at a bigger company who has spent a lot of time doing this in both settings)