Other advantages to a rangefinder are:

Easier low-light focusing, because you are not dependant on the maximum aperture of the lens.

Better, smaller, often less expensive, wideangle lenses, because you don't need a retrofocus design to get around the mirror.

Leaf shutter lenses will sync at any speed, so if your camera uses leaf shutter lenses, you can use fill flash in bright daylight without the complex electronics required to make a focal plane shutter do that trick.