Depends on how much crap it goes through to get from one place to the next, and if you plan to fly to gigs.
i'd say get a flight case, cause you never know when you'll need it, and that way you don't have to invest in somethin new when you do need to fly
they look cool. make your gear look more "professional" sometimes. if youre just going from like band practice to home then you dont NEED one. a flight case is usually more for a serious touring band...