I worked for a startup where it felt like I was being crushed. Most of my co-workers and people running the company were average to poor, we didn't have a choice in technology and I saw a person who downloaded porn all day, was barely at the office and was caught with child porn on his computer promoted to senior management.

That's not a good enough reason. I worked for a large company and know others who work for large companies and find the work very rewarding.

The choice of what experiences will best suit you on your way to starting your own company is more personal than black and white comparisons. Not all big companies are evil empires designed to crush you (e.g. Google) and not all startups are rosy playgrounds for engineers.

In the end, as expressed by several people here, it's a personal choice that has to fit your own values and which experiences you want.