If you have impeccable home care with brushing and flossing, the type of brush you use does not matter.
Since most people aren't that good with the brush then the electric brushes can be useful.
Studies have shown a 40-50% plaque reduction with patients using an electric brush vs manual toothbrushing.
The key part is that you have to use it and use it properly. Sonicares come with an instruction book on how to brush with it. It is not the same as a regular brush.
One tremendous advantage is with the upper end models, they have a pressure sensor that detects if you are pressing to hard with the brush and power down under excessive force.
New sonicares and the Oral B Triumph are excellent and I do recommend them to all my patients.