Airtel is the best network in India until Jio entered into the ring. But still it is the largest network.
Coming to prices it is very expensive Airtel provides any service with high cost so if you can't afford you don't buy it. It's better to buy idea or Vodafone if you want low roaming charges.
But when it comes to data speed there is no other network I have seen is better than Airtel the data speed in urban areas reaches UpTo 4Mb in rural areas we will get signals every where with a data speed of 2 Mb soon in order to stay connected this is better network than any other
And coming to international roaming the charges are too high so it's better to choose any other network
And my sincere advise is that Airtel is better choice.