My experience with (2) larger companies, and confirmed from conversations with friends, is that while you tend to have more support, you are often placed on individual siloed teams where you stay for years. I think the key benefit of smaller companies is that you can work across so many different aspects of the application. Process also tends to be less burdensome so you are able to devote more of your time to the text editor writing business logic.
Still, my experience and my circle is limited so I suspect some might have had the opposite experience.
I was interviewing at a megacorp a long while back, my interviewer was solely responsible for the pie charts in some old application. He mentioned in the interview that it was totally feasible to run your own startup on the side.
An acquaintance of mine worked at Google for one entire year on the functionality of one single button in GMail (I don't recall what it was specifically). He was very disappointed, left and launched a startup.
Still, my experience and my circle is limited so I suspect some might have had the opposite experience.