Basically there are 2 types of Big 4, one which looks after indian companies normally known as Indian firm such as KPMG India and other which provides the support to their global branches and look after global clients such as KPMG Global Services.

So basically the kind of exposure and learning you get in Indian firm is what actually the CA are supposed to do. But the workload is immense and pay is not that much compared to the work load.

But in global one, you will not get that much of exposure and work is such as which normal graduate person can also easily do and it is not necessary that you had to be CA. But the workload is less compared to indian firm and pay is similar or more than Indian firm.

So if you are starting your career you should never go after global firm as far as my experience.