Mine is a dual connection household, I use one Airtel connection as the primary and the secondary MTNL one for backup. However, it seems I will need to change the order of those soon. Lately, airtel seems to have very odd bandwidth counters which always seem to never match up with my router connection monthly counters. The difference is more than 20-30% month on month [adding both up and down counters!], which means that this is deliberate. So a consumer like me pays for 75, gets 50 and well is forced to buy these Smartbytes packs to fill up the deficit for nearly one third of the month!
So Airtel in my opinion is stealing my bandwidth which after many many complaints has been not taken care of! I can only view this as a systematic accounting corruption on their end.
In any case, I have come to the conclusion that MTNL is far better in these matters for the NCR region and see no use of using Airtel as the primary in my case. Have you experienced the same? Do let me know?