Airtel is a World no 1 telecommunication company for their service into all over the world. It have different branches through all abroad. Airtel has big company in the indian market. They gives high speed of network in all over country. Airtel has approved that their 4g network has high speed than other 4g companies.
I am also using 4g sim of airtel at my home and I have also little experience about it . it has more speed than compare to the other 4g sims .it can possible only for their smart network in the all over world .
I suggest you for using airtel 4g sim only not for speed network. They now giving insurance policy of 1lakh for accident. Its is very good uportunity to have branded airtel 4g sim.