Though 4G first came out with airtel as its service provider. But the service it gives is awful.
I do not know about other cities but in my city even being a metro the tower reception of airtel 2G, 3G as well as 4G are very very poor.
I personally use an airtel prepaid and a 4G dongle. Maximum time my gmail is even going round and round.
I never get to see all the bars standing up high and giving me a 4G speed, paying so huge for 4G plans and not getting proper tower and thus speed is really sad.
I personally am goin to get rid of airtel soon and would not recommend it to anyone who seeks knowlege from me.