How does Orwell compare Animal Farm under Napoleon's leadership to its exploited state under Farmer Jones's rule?
It's the same thing ... perhaps worse. I say worse because under Jones the oppression came from another species or class. When Napoleon takes over he is one of their own and he offers them hope that things will be better with new leadership. What the animals finally wind up seeing is that the problem isn't with who is the leader, but with the whole problem of leadership. They also learn that what those who seek to lead them say often has no bearing on what actually happens in the end. At least Jones made them no promises; Napoleon offered them a better life, an earthly paradise, and delivered them Jones II.
I agree. It's much worse especially since the propoganda that was used by the pigs to convince the other animals that they were being mistreated, abused, etc. is the same things that they themselves are doing to their own kind. In fact, that is the exact definition of irony. The outcome is expected to be different because of the change that was brought about but it was more tyrannical and hypocritical than before.