Firstly, startups have been an absolute delight. I very carefully chose the company and hence my boss and my co-workers and love working with every engineer on the team. It is a pleasure coming into work each day and I often cant leave because I'm excited about my work.
I have a lot of authority over what I build a much of it is "close to the metal" rather than some side system. I get to see the whole slice of cake from conception all the way to sales and client implementations and participate in all of it. At small companies, as an Engineer, I learned how to build a successful product and learned all the steps from inception to sales and production.
At every big company I was at, there was more specialization and lots of process. Process was necessary at that size. There was also a great deal of inter-departmental politics and incentives were usually not aligned at big companies, sometimes incentives across departments were even orthogonal. I spent 30% of my time on process and communication at big companies and it went to 80%+ once I was a senior executive. I made a lot of money there, but I think it was to compensate for having to deal with the inner workings of a big company (and being able to be effective at it.)
At big companies, I learned how to turn the gears of organizations and learn how to make globe-spanning change effectively.
To be fair, I took a big pay-cut to come to a startup as an Engineer. I'm happy with the choice. I dont think there is any silver bullet out there, but it is important to understand what you get with each choice. It is also important to make that choice with full intent and not be fooled or brow-beaten by anyone.