If you are talking about British law
Merits to Britishers was - The system would ensure regular flow of revenue and zamindars would invest in improving land quality
Demerit were - 1) zamindars were not interested in improving land
2)when the prices rose and cultivation expanded ,the zamindars benefited whereas no profit to Britishers.
3)revenues were too high for peasants to pay to the zamindars and if failed
they were evicted from land
hope it was what you wanted and helped you