My first Sim is Vodafone I have use its also long time.This is one of the best mobile service provider. Vodafone is the only network that is available in almost all corner of India.
We find Vodafone stores at everywhere. Vodafone call charges and data pack rates are also good and reasonable. Vodafone net was good speed to use.
So many people used Vodafone. Vodafone India provides services on basis of 900 MHz and 1800 MHz digital GSM technology.So I recommended you to use Vodafone