It´s a speed up because disabling EFB stops the rendering of the mayority of the needed graphic effects (excluding the exceptions LV referred to).
Rig 1: Windows 10 Home | AMD A6-1450 @ 600/1000/1400 MHz | AMD Radeon HD Graphics 8250 | 4GB RAM | HP Pavilion TouchSmart 11.
Rig 2: Windows 10 Pro | Intel Core i7-2640M @ 780/2800/3500 MHz | Intel HD 3000 Mobile | 8GB RAM | Dell Latitude 6320.
