Dude there are two reasons why MTNL seems to provide speeds close to what they promise aleast in Delhi.1) Sync Rate policy of MTNL Delhi. They have taken into account the PPPoE overhead which eats up abt 16% of ur bandwidth. Say u have a 256 K line and the telco syncs u at 256 K only then the actual speed that u get is 256-256*16% = 215 Kbps. It seems MTNL delhi are aware of this loss hence they increase the sync rate to compensate for the loss i.e. the sync rate for 256 K line is 288 Kbps and for 512 Kbps is 576 Kbps. But MTNL mumbai doesnt follow this policy and their speeds are not close to what they advertise unless ofcourse someone has been synced incorrectly. Airtel uses PPPoA which has an even higher overhead than PPPoE which means that u can easily deduct abt 17-18% from ur sync rate, say if its 256 K then spd u'll get is 212 Kbps or if u have 128 kbps it'll be around 106 Kbps.2) MTNL doesnt have many Untld plan users coz it has a very expensive unltd plan, that also available only in delhi, infact with telephone line charges included (which are mandatory) it costs Rs.1653/month even if u use ur own modem. On the other hand Airtel definately has more unltd users coz of its cheap (comparitively) Unltd plans - @ 64 Kbps; 128 Kbps ; 256 Kbps.We can only compare the two when MTNL comes under similar load through introduction of cheap unltd plans and still manages to have as many satisfied customers as Airtel. Therefore, at this point i would say Airtel is a better ISP than MTNL.PS chk the BSNL forum Airtel is rated better than BSNL