Which is better, flat or shiny laminate floors?

Bette in what sense: slippery, cleaning, showing scratches, for children?

Shiny floors are more vibrant and visually stimulating. Also, they hide the appearance of dust, dirt, scuffing, wear, scratching, etc much better than a flat finish. It would be easier to clean and maintain with shiny floors, but over all, you should pick any interior decoration based on your own visual enjoyment.