CDMA - TATA Photon, Reliance, MTS & BSNL EVDO.
GSM - Idea, BSNL and many others.
CDMA based operators are all good.
GSM max speed you'll be getting is 256kbps under EDGE but once 3G comes you'll get around 3mbps. BSNL/MTNL gives you 3G.
I would recommend you to take a GSM Datacard & use a operator you like. If you have problems with them you'll be able to change to any other unlike CDMA based ones.