Let's look at it more practical way.
Big firms = Financial security. For all. Long term. Startups = Financial Risk, even for workers.
I have seen many fancy startups who are trying to be edgy offering progressive incentives and doing stuff to brand themselves cool on social media. But in reality, they struggled meeting deadlines, bad product or service and employees are just adopting edgy habits instead of helping company. Lot of startups wind up due to such practices.
Many startup founders and cofounders do build a good product and become successful. I am not denying the possibility of success. But startups are not the place for learning good coding habits and holding financial security for career.
If you have even seen the days of 2006 to 2008 depression time. You'd choose big firms instead of startups.
Build your experience. If you build it on the established firms, you're more likely to keep the success horse running. People can argue all they want but the startup is a risk. Often a risk worth not taking if your goal is to be stabilized in terms of career and finances.