The Advanced Spotlight is custom coded light, written specifically to render faster and give more control over your lighting.
Have you ever had a scene which rendered quickly, until you added transmapped hair, and then processing slowed to a crawl? This spotlight allows different surfaces in the scene to use different shadow quality settings. Now you can set the hair to use fewer samples than other items in the scene or have the light simply ignore that surface completely.
The light has four falloff modes, an inner angle for adjustable 'hot spot' softness and it supports procedurally blurrable gobo textures (aka. gels, cookies, filters). The Advanced Spotlight also works as a point light.
Because of all the features and extended control options, the light does have a bit of a learning curve but, with use, I feel it will become your go-to light any time a spot or point light source is needed.
To learn about all the lights capabilities see the Detailed User Guide.