Aspheric

An aspheric lens' greatest strength is throw. There is no other collimation method better for this task. In fixed focus designs where the lens is set for maximum throw there is little to no spill light and no spot to spill transition to speak of. This has its drawbacks but also benefits depending on the application. The lack of spill light means you have a reduced sense of perspective of the environment as you cannot see as large an area at any given time. There are however some adjustable beam aspheric lights that can have a nice combo of super throw but also a flood beam all in one light.

There is benefit to this highly confined beam. In security or law enforcement applications where stray light would be potentially dangerous or disturbing to the environment these lights are the perfect fit. For instance when spotting near a road a typical TIR or Reflector light's spill light can blind or distract drivers. Searching in neighborhoods is also easier with an aspheric type light as you get high intensity but can avoid disturbing the occupants of the buildings you are searching around. You also reduce the chance of losing night adapted vision which can be crucial in certain tactical situations.

One other benefit to this confined beam is for hunters who would scope mount the light. You can have a much smaller light than you would otherwise have to have for a given intensity and far longer battery life for equivalent throw.