To put it simply it is a massive gamble from the protagonists perspective. If the rebellion fails while they are involved, then of course they lose everything they already have as part of Ikaanos's privileged landholding class, an ignoble execution likely waiting in their immediate future should the rebellion be crushed.
But if the rebels win, well you have an in with the new government, likely quite a considerable one given your role in their ascent, and other factors involving your relation with Aria. You could go from 'merely' a landholer, if a very rich and powerful one (with a private army) to suddenly being a principal figure in the rebellion, a revolutionary hero and a close 'confidant' of the woman likely to take power in a post rebel world.
As for if there are changes, well I am not 100% sure exactly what is involved, but I know back when the daily event and political system was first being shown off, they showed some events for a post rebel victory and mentioned that which events proc depended on certain factors like Aria's corruption, so presumably it does make some tangible difference in how the state ends up being run after the rebellion succeeds.