I have been using airtel mobile sim for last 5 years.It is very good simply because network is always available. whereever you go network is availble.
There are many feature like airtel money that is very helpful to trasfer the fund and it has many other feartures as well. Friends I will tell you to buy airtel sim and use it. You will never get disappointed.Most of my friends are using airtel sim they all are satisfy with the service that airtel is providing