Rulley

Hey guys, I need some advice here on an issue i heard on someone's stream. From what I understood is that, the higher dpi the more sensitive the mouse, hence it's smoother. So what if instead of playing on 400dpi with 10 sensitivty, why not play on 800 dpi with 5 sensitivity? You still have the same sensitivity, but your mouse is a lot smoother. Is that true? or bogus? Thanks!