that depends on your style and your game. I prefer to use layers instead of layouts. E.g. I have one layout for the menu (starscreen, highscores, options, ....), one for the game structure, and one unuse layout to place a copy of any sprites a might "create" later in the game(I call it parking space).
I work a lot with anchors and if you load a new layout it needs to adjust everything sometimes. I use a black-screen-fading between layout changes to avoid uglyness.
You just have to be carefull if you have many sprites. I guess each layout loads the sprites needed so your total memory usage increases if you put everything in one layout. It really depends on your games and the platform you are targeting.
In general, if you want fast results, I guess putting everything in an extra layout is easier. If you work with layers you need to disable visibility and maybe a groub to deactivate touch/click inputs.
I prefer layers. It makes it more fluid on mobiles, but would be nice to here other opinions on that too.