Vantaggi
Big4 experience is a plus on your CV. There are some good people there that you can learn a lot from. Learn a huge amount about how businesses run in a very small amount of time. Big name, high profile clients, sponsorship of professional exams, competitive benefits package.
Svantaggi
Not enough recognition paid to junior people who are actually doing most of the work. Too much office politics. The apprisal system seems to be a sham, no one takes it seriously and it's all corporate talking. (Once a manager gets an idea of what he would grade you, you would have to share your lottery win with him before he will think otherwise, whereas another associate with whom he is friends with will consistantly be graded better) Sitting next to a partner knowing what the total average pay packets in a big 4 firm for partners is compared to your own.