I don't know the best, but I could inform you something.. I was using data card of BSNL and when the device got damaged, I went to buy for a new one. But the same was costlier around 3000 Rupees and they could give only 6 months warranty. I couldn't waste money on that and it could accommodate only sim of BSNL.
Then one of my friend told me about the unlocked datacard - in which we could use sim of any data provider say BSNL, vodafone, airtel etc. I bought it from ebay
Huawei E1752 Orange 3G usb modem Data Card 7.2Mbps HSUPA 3G+ (1700 Rupees; 6 month warranty)
Here goes the link; it is working fine for me since October 2011