In smaller company you are closer to person with the decision power. It is much easier to build closer relationship and have high visibility to avoid being laid off.

Companies, of all sizes, are run by people.

If those people are assholes, the size of the company doesn't matter, your employment in that company will suck.

While that is true, if any given person has some X% chance of being an asshole, the more layers of management there are above you, the higher the chances you are at the mercy of at least one (and possibly multiple) asshole(s).

You could use the exact same argument in the other direction: the more layers of management there are above you, the higher the chances a high-level managers will protect your team from armageddon. Sometimes, it's only a matter of a single email or a chat with a CxO.

I stand by my original point: no obvious correlation between company size and quality of life inside it.

True, the difference is you are more likely to get the experience you've heard from reviews in a small company vs complete unknown in a big company (may be great, may be crap depending on your line of management)

In my network we keep joining the same (relative small) companies because we roughly know the culture we can shape and create an environment