But to me, they are the same. After you prepare the toppings for chirashi sushi, you can scatter them any way you like in a bento box. Or layer them in parallel, vertical or diagonal lines.

From Marc, Salmon Menchi-katsu: deep-fried breaded salmon cakes! Maki cooks up a delicious Chicken-nasu bento with her 3S sauce plus one. Also, a look at Taiwan's "san-bei" or "three-cup" cuisine.