Something most people don't think about with large companies:
They aren't monoliths. Your experience could be totally different in a different part of the company. 300k people is going to create a ton of variance.
That said, I've found the larger the company, the more politics matters. And the more politics matters, the less your performance matters, and the more the other things matter.
Personally, if given my way, I might never work for a company over ~50 people, again. (I'm working for a small firm now. And pretty happy overall.)
The ability to walk up to high management and get a fairly straight answer on what is going on, is something you simply can't get in a 300k company.