Pros
EF is a big-and-getting bigger company with a strong foothold in the private language education industry in China. As such, they are very careful to do everything by the book. Working for EF, you can be confident that you're adhering to all the government regulations as far as visas and the like are concerned, which is a big deal when living and working in China. EF is also a great place to work if you're looking for career development. There's a lot of room for growth whether you want to continue as a teacher, move into management, or move in another direction within the company. If you're looking for more than just a gap year experience and want to develop your career in this field, EF might be the place for you.
Cons
If you're not looking for career development and simply want to spend a year abroad making as much money as possible for as little effort as possible, EF might not be the place for you. EF (especially Kids and Teens) is a lot of work, not a lot of vacation days, and, while the pay is more than enough to live comfortably, it is not nearly as high as some other ESL jobs in the same locations. And while individual centers within the EF community do foster a sense of belonging and family (I have found this at my own center), EF as a whole is definitely a for-profit company and you can feel that sometimes.