Let's start simple. There are two physically identical islands, Alpha and Beta. There are two agents, A and B. Initially, A lives on Alpha, and B lives on Beta.
Under "Open Borders", each agent has the right to move to either island, if he wishes to.
Under "Forced Emigration", each agent has the obligation to move to either island, if the other agent wishes him to.
Which is better?
If you like, you can assume they take turns to play the game, with one play per year.