Best answer: The only difference, besides possible color of the device, is that the 700 uses rechargeable batteries and the 650 uses regular AA batteries (unless that has changed to AAA). I have a 650 that we have used for years. It would be working better if it hadn't been dropped to often, and it requires new batteries about once every 2 to 3 months depending on use. As far as I can tell the 700 is actually a discontinued product, so I am surprised to see it here, they must have had some remaining stock to liquidate. You will not see the 700 on the Logitech website.
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