A bowl can be less messy, and ylou can get the lather you want before you put it on your face, a bowl can literally be a plastic takeaway container, the round ones about 4-5" across work, why not try it like that and see how you go, then there are scuttles, a bowl with a water reservoir surrounding it that will keep your lather warm or cold depending on what you like.
You also need a bowl to make uber lathers, whee you mix soap, cream and usually glycerin together to make the lather.