I somewhat disagree with the idea that a Big Corp reduces your learning opportunity. I work for one of the big companies, and one benefit I don't see highlighted frequently is changing specialties. I have worked in 4 different job families over 6 years. If you do work for a Big Corp and you're an effective employee, you can pretty easily work on jobs at the border between the job you have and the job you want. This may be specific to my employer, but I've been able to find ways to demonstrate my (on the job learned) knowledge in a field and get a job I find interesting.