Which is better for menus -- layouts or layers?

This is a general question for experienced C2 users.

In designing your game, do you use different layouts or layers for your various UI elements if you have several: (Game Start, Instructions, Customization, Leaderboard, Signup, etc... ) -- so far it seems like different layers are better if you are keeping the same background/some objects (and the tuts seem to keep UI on separate layers) ... but I am still curious about when it is better to use layouts.

Is there a preferred approach? ... at what point do layouts make more sense?

Many thanks for your tips!

Basically, everything that is ingame is better on layers, pause menus for exemple are better done that way, however, a menu that is not tied at all with a level would be easier to do inside it's own layout, without every other assets being loaded with it (title screen menu for exemple), however if a menu can be accessed in the level and also the title screen, you can have both (an option screen for exemple can be availiable on both).