Different types of data card available in market.

Mtnl 3G Data Card decent coverage in Delhi & Mumbai with switch over to edge/gprs data whenever 3G coverage not available. With roaming agreement with Bsnl …. roam on 3G network in Bsnl areas. Speed is 3.6mbps and 2.0mbps upload speed.
Available in both prepaid and postpaid with affordable plans.

Bsnl 3G data Card available in all India except Delhi & Mumbai with decent 3G speeds and congestion free edge network wherever 3G data network is not available. Similar roaming agreement with Mtnl in Delhi & Mumbai. Speed is 3.6mbps and 2.0mbps upload speed. Available in both prepaid and postpaid with affordable plans.

Tata Photon plus data card works on evdo network for 3.1mbps download speed and 1.8mbps upload speed is available in more than 33 major cities while it works on 1x network in rest of cities where Tata Indicom has coverage. Available in both prepaid and postpaid with little costly plans.

Reliance Broadband Plus data card also works on evdo network with same 3.1mbps and 1.8mbps upload speed. Available in major cities only with support of Reliance cdma 1x network where evdo coverage is not available. Available in both prepaid and postpaid however charge are exorbitant.

Mts Mblaze data card is also evdo based card with 3.1mbps and 1.8mbps upload speed. Totally congestion free network however available in limited areas and available in few states. They regularly launching in new states so expect good coverage soon. Available in both prepaid only with affordable plans.

Airtel 3g data Card is a 3g card but only works on edge/gprs network as Airtel doesnot have 3g network coverage currently. Still all India Edge network gives decent speed. Available in postpaid only with unlimited plans.

Vodafone 3G data card vodem is similar to Airtel card on edge network as vodafone also doesn’t have any 3g coverage in India. Plans are little costlier to Airtel with similar speeds in edge network. International roaming also available with this card.

Idea Netsetter is 2g data card on prepaid with cheap plan on Idea 2g edge network and not so good coverage in all cities. However cheap with unlimited plans also available.

Before buying check coverage/speed where you’ll use the card most. Also if you roam a lot then do keep in mind if network is available in the state you visit. Next check how much data would you use and compare the cost higher data package. Do remember 3g/2g card are mostly unlocked where you can use other 3g/2g operators sim card. While the evdo card don’t have sim slot are mostly locked.