Reliance Jio 4G offering you 4G VOLTE which means Voice over LTE means your calls getting the equal priority as data. When you are talking to someone on the phone, and at the same time you want to check your mail, then you can check it or surf the internet at the same time. According to Mukesh Ambani Voice calls is completely free in jio. You will get 4G speed in every place because jio is only providing 4G network not for 2G or 3G, so it means network never switched from 4G to 2G or 3G. They are also providing you data at very cheaper rates. Reliance has a license of Pan India spectrum which means you can get Jio network in whole India. You can compare Reliance 4G Internet Packs and Jio 4G Internet Packs , both are rival companies . You can compare state wise plan.
Airtel 4G uses 2300 MHz spectrum for BWA (Broadband Wireless Access) in 15 telecom circles of India (out of 22 circles), though Airtel has also bought 97 MHz spectrum in the 1800 MHz band, While, Reliance holds the license for 2300 MHz spectrum all over the country plus, 850 MHz spectrum in 10 circles and 1800 MHz spectrum in 6 circles for all kinds of services. Keep in mind the fact, that 1800 MHz band is one of the most popular bands for deploying LTE services across the world, due to considerable advantages over 2300 MHz band. Around 44% of global 4G networks are used over 1800 MHz spectrum.
You might also want to check Airtel 4G Internet Packs which one of their rivals Telecom Operator and current at no. 1 position in India.