I have been using both Airtel and Vodafone for years.
AirTel’s network is congested hence quality of service particularly data service is not the best considering the premium price they charge.
Vodafone’s network is not that congested compared to AirTel particularly data service which is faster than AirTel.
During the recent flood in Chennai only BSNL, AirTel and Idea managed Vodafone went down completely for almost 7 days for the premium price they charge!
During emergency you can’t rely on Vodafone otherwise ok.
Their customer support is the best!