I am using airtel sim for the past 1 year. The network is really good compared to other sims, and this is its only advantage. The 4g is really fast and can be recharged easily online or in retail shops.
But the 4g offer rate is very high. Just 2gb of 4g for 3 days cost around 400rps till relience launched jio.
I would recommend u for buying airtel just for calling purpose. Airtel 4g is not worthy and I am sure u will regret if you use airtel for internet.