[java] When to use actors in libgdx? What are cons and pros?



I'm writing simple solar system simulator. This is my first libgdx project. I'm using a Stage and Actors for the main menu and is pretty handy especially touch events handling. But ... looking at the examples i see nobody uses actors in actual game logic. I wander if i should use actor as a parent of planet class or just write my own class tor that. The planets won't be touchable and they will be moved only between the frames so the third parameter of action MoveBy will have to be time between frames. That are the cons. What are the pros for using Actors?