both are anroid devies.both have 8mp cam but samsung galaxy s2 has face/smile dectection its has good battery back up..my friend is using lg optimus but is does not have battery back up...my suggestion is to take samsung galaxy s2
3g is best as far as speed is concerned .2g is best as for as cost is concered... example airtel 3g internet plan 60mb 3 days validity 60rs only...where as 2g internet plan 150mb 3days validity 16rs only