Scientific research has shown manual toothbrushes to be as effective as powered toothbrushes, considering you are using proper technique, eliminating plaque from all surfaces of the teeth and brushing a minimum of 2 minutes. With that being said, only a very limited percentage of the population who are using manual toothbrushes are brushing to this standard. As a dental hygienist who sees an average of 35-40 patients a week, I can speak from experience that patients whom I recommend power toothbrushes have less plaque, tartar buildup and bleeding, as well as overall improved tissue tone of their gums.
There are two main types of electric toothbrushes on the market: sonic and oscillating. The sonic brush heads are shaped like a manual toothbrush, and use back-and-forth (side-to-side) motions. The oscillating-rotating brushes have round brush heads that rotate in a circular motion. Both styles are efficient in gingival (gum) stimulation & overall plaque removal.
When shopping for a powered toothbrush, look for one that plugs into the wall and charges. Although more cost effective, battery powered toothbrushes tend to be less effective as the batteries age.
Powered toothbrushes are an important piece of the oral hygiene puzzle, however they do NOT replace the need for plaque removal in between the teeth. The use of floss, floss picks, proxibrushes, etc. are still necessary to remove harmful plaque and bacteria in between the teeth, not only for a healthy mouth but for a healty body overall.