No it isn't. I, and many I know, would never trade away 100+ hours at a namebrand investment bank/PE firm/consulting firm to work 100+ hours at a startup. It's not what I would recommend nor is it what many people I know would recommend, some of whom are billionaires. The constant advice is to always work at the best possible opportunity the first few years of your career, then step into entrepreneurship. You'll then have an idea of things actually work in the world. And I say this as someone who went the other way around (startup first before working in corporate).