neither will be 100% accurate, both use an accelerometer to work out the number of steps taken. You may as well take the average of the two rather than relying on one or other. All pedometers in fitbands, smartwatches and smartphones give widely differing outputs and should only be used as a general guide to daily activity levels. Even the most expensive ones are inaccurate, the BBC tested a whole load of them on Michael Moseley's series.
