The point of the sumo style deadlift is to try to reduce the range of motion of the deadlift movement to allow more weight to be lifted, but it depends on the individual whether one provides more mechanical advantage for your build and current level of development.
The opposite is snatch grip deadlifts from a platform or using small diameter plates, to maximize the range of motion and make the deadlift movement as difficult as possible. This allows you to produce more load with a lower weight, possibly reducing your chance of injury while maximizing muscle building stress.
