People ask if these various types of electric toothbrushes are worth buying. Let me first say that a dentist friend of mine, Dr. Shah, starts with every new patient by explaining how to brush their teeth. He estimates that 90% of people don't brush their teeth properly.
I use the Sonicare Pro Health toothbrush. What I've seen is that there is a significant benefit to using an electric brush, and ideally a sonic one. There is no way you can move your hand fast enough to replicate the action of these brushes, and people have found that they have much easier dental cleanings when they use them. This was my experience when I switched to a sonic toothbrush. And easier cleanings is reason enough.
There is an adjustment period with these brushes. The first time you touch your tooth with the vibrating plastic rather than the bristles is a real eye-opener. But you'll quickly learn to manipulate the brush properly and the result is a great, clean feeling. They are also excellent for brushing your gums and tongue (which you should.) You also need to wrap your lips around them in a very specific way, not the wide-mouthed approach that you can use with a regular toothbrush, otherwise you will have toothpaste spray all over the bathroom mirror.
My particular Sonicare has a special feature that disinfects the brush portion with an ultraviolet light (I'm a bit germ-phobic.) I have tried various Oral B brushes, and am less impressed. Their Triumph felt like a jackhammer. And the Ultreo, the most expensive of all, designed by the former Sonicare inventors, is not as impressive as its price. And I can't figure out what the rubber block in the middle of the bristles is for. And three of them went defective on me in a row.
Don't forget to change the brush every three months or so. If the bristles are starting to bend, it's time.