Layouts allow you to manage your graphical memory, only sprites that are used in any particular layout are loaded into memory. It will allow you to have a greater variety of textures between layouts.
Having everything on a single layout might be simpler to execute, but you might run into memory limitations. Depends on the scope of your game.
Also "time" does not pass across layoyuts, which may be a consideration.
Alright, thanks for the great answer!
Except "time" which isn't a problem for me, are there any more limitations?