I am using loop connection. It is pretty cheaper to use this connection and has a large number of services with good GPRS. Its easier to form group of friends. SMS is at cheaper rates jst 10paisa which none of the other networks are able to provide till now. It has a good network connectivity with hardly any range problems.
The only problem is sometimes you have to wait longer for customer service helpline to answer you. Also it lacks 3G services which most of other networks have.