I looked at the angular-ui modules because I need to implement a grid.
I saw that there is the stable ng-grid and the unstable version ui-grid.
Which version should I use?
Are they very different or hard to switch?
The github repo says that all development will happen on ui-grid (ng-grid 3). That means ng-grid has become a legacy grid. ui-grid is stable enough to use in my opinion and the only reason to use ng-grid is if you already started with it. New projects would be better off using ui-grid. They also claim that the performance of ui-grid is better than that of ng-grid though I haven't tested that.
UPDATE:
A stable version of UI Grid 3 is out which means that it can be used in production applications. On their documentation site, they have a guide on how to upgrade from legacy ng-grid. See Tutorial: 099 Upgrading