Everyone has their own individual needs. Some will recomend Dusk Till Dawn lights - Keeping the whole area lit overnight, Good if you wish to light up a doorway etc for visitors. Floodlights, I Believe are more of a security feature due to the fact there is no light and a sudden bright light can attract attention therefore putting off potential burglars. Down side is as stated previously, if not set up correctly the slightest movement with wind or passing people/cars can trigger them. You then get Pi**ed off checking outside everytime they come on.
Some floodlights also come with an internal buzzer so when they are activated if you don't see the light come on you will hear the buzzer.