I actually was in a big IT company, and you'd think that you'd be able to work in different teams and get different experiences, but sadly it's not that easy in reality. With big companies you typically have too much red tape to wade thru when changing teams, each team acts like their own isolated unit and they don't really work well together. Also, the higher up you are in your role, the harder it becomes to get secondment opportunities since they may be unable to find someone to take your place. Also, you're far more siloed in a big company, so say if you've been hired as a desktop engineer you won't get to work with server or networking stuff, whereas in a small companies you typically have broader job descriptions and responsibilities.