I have, I went from a baby bell to a small company. I've also worked at a mix of small and large companies.
Large companies do have company politics, some more than others, but so do small companies. At small companies, the politics tends to be out in the open. Also, you know who is sleeping with who. I'd call this a wash.
Large companies tend to have policies and procedures, so you can get things done, it's just sometimes arduous. Small companies, you can just go ahead and do stuff. But sometimes, if you hit on a sore spot or annoy a higher-up, you get arbitrarily stopped. Things do move faster at a smaller company, unless it's something they've experienced pain over in the recent past. Then, they just don't happen. I personally would give large companies a small edge here, but it's possible that a less dysfunctional small company would be better. I just think they're rate.
Big companies have real HR departments. Yes, HR exists to shield the company from its employees, but that means legally-vetted procedures. Small companies HR is hit and miss, and sometimes obvious transgressions don't get punished, but swept under the rug. Sometimes weird bad things happen and HR doesn't blink, sometimes weird good things happen, and HR doesn't blink. But weird HR related things happen more at small companies. You've got to be aware of that, otherwise, you'll ask out the RMA manager who is secretly sleeping with the Director of Something, and get in trouble.
To my mind, big and small companies are pretty equally horrible. In big companies, you suspect that upper management is a pack of insane criminals profiting via corruption. In a small company, you know for certain that upper management is a pack of insane criminals.