Well, I used BSNL 3G, Vodafone 3G, Vodafone EDGE, Airtel EDGE and Photon+
Photon+ gives approx. 256kbps though they advertise upto 3.1mbps(which is correct in marketting sense
). Browsing along with few downloads about 100MB and all is ok.
Vodafone EDGE gave around .22mbps on speedtest and for browsing it was ok, but fails when browsing multiple sites and loaded sites. General facebook, orkut, TDF will be ok.
Vodafone 3G rocks..!!
But if you are looking for downloading then the present tarrifs are not your cup of tea.
BSNL 3G is also good but not stable in comparison to Vodafone 3G, I mean speeds keep fluctuating, overall it's ok. Again look at the tariffs.
Airtel EGDE is same as Vodafone EDGE, for browsing it would be ok.
So if you are not looking for donwloading you can go for 3G, otherwise you need to stick to Photon+ and all, as under EDGE downloading would need much high patience, except few MB songs and all.
So speed wise 3G > Photon+(and others) > EDGE.
Note : That depends on your area, in some areas, people gets much better speeds on EDGE. So I'd highly suggest you to test before getting one.