The similarities: Both regimes are totalitarian states, one run by a Monarchy, one by a Dictatorship. They repress the population by a lack of education, brutal work conditions and lack of food. This keeps the working animals looking for survival more than anything else. At the end, when the animals cannot tell the difference between the pigs and the Mr. Jones, it is meant to represent that the other animals just traded one harsh reality for another, and their lives are no different
The differences: While Mr. Jones represents a top down type of repression, with Napoleon in place, the animals feel, at the beginning, that they are in control of their destiny. At the end they find out differently.