Like many things the answer isn’t perfectly clear. However, many studies have been done on each one and results have been reported with each maneuver. I’ll address each one below.
1) Brandt-Daroff maneuver (this example is for the Right side):
This maneuver consists of sitting upright with your feet over the side of your bed, lying on your right side with your right ear against the bed, or with your head turned to the left. This first step brings the BPPV particles in your semicircular canals about 1/2 way around the bend of the canal (causing vertigo). Then sitting up. This allows the particles which have moved 1/2 way around to begin to fall back down the same way they came from. Then lying down on your left side with your left ear against the bed or turned a little to the right. This doesn’t really affect right sided particles as it puts the canal in a horizontal position but may stimulate symptoms in left sided BPPV if you have it in both ears.
What this maneuver does is create and stimulate the worst of vertigo in patients with BPPV but doesn’t actually treat the underlying cause. As such it is useful to habituate yourself to your vertigo. However, in light of the following two maneuvers I see no need to ever conduct this maneuver.
2) Semont maneuver.
There are two important differences between Semont and Brand-Daroff maneuvers. 1) Speed and 2) keeping your head pointing toward your left shoulder. Lets go over the example again for the right ear.
Start sitting then lie down on your right side. It is important to turn your head to the left and look up at the ceiling. This will stimulate BPPV. Stay there until the vertigo passes. Now QUICKLY sit up and lie on your left side but KEEP your head pointing over your left shoulder during the entire time. You should now be facing down to the ground. Do not turn your head. Wait there until any vertigo passes. Then sit up.
What has happened here is that the particles move into the bend of the semi-circular canals during the first positions, then when you quickly sit up they don’t have a chance to fall back. Finally, by looking towards the ground on the other side they fall out of the semi-circular canals all together.
Since this maneuver requires speed it can be difficult for the elderly. However, it requires less neck flexibility.
3) Epley maneuver.
This maneuver and the Semont maneuver share the beginning and ending head positions relative to gravity which is why they both work. (start on back with head facing ceiling, end on other side facing the floor). The Epley maneuver is not speed dependant as it doesn’t rely on momentum to carry the particles over the hump of the canal and down the other side.
The maneuver begins on the back with the head turned to the right. In the second step the person rolls their head to the left, then up onto the left shoulder and looks to the ground, then sits up.
There are a number of devices to help perform the Epley maneuver and most publications now recommend the Epley as the first choice of maneuvers unless there is some contraindication. To my mind there is no role for the Brandt-Daroff exercises unless both the Epley and the Semont maneuvers have failed.