What are the main differnce between IGMP v1 and IGMP v2 ?

IGMPv2 is better than IGMPv1.In IGMPv1 two messages were introduced group membership query(send by router)  and membership report(send by host) .No mechanism for a user to leave the group , so a user have to wait up to 180 second even when it does not want to receive the traffic.

In IGMPV2 one new message was introduced that is Leave message.

Leave message was used to remove this leave latency.

One more difference is in IGMPv2 you can change MRT(Maximum Response time) which is default 10 sec in V1.