The Withings scale is a bit larger at 12.8 inches square, and for someone with big feet like myself, it is a bit easier to use. It also has little arrows that light up at the corner of its display if you are not centered; this helps ensure that you are in the right position to get consistent readings. The Withings scale also has a larger, brighter display, making it much easier to read without my glasses.
Compared to the Fitbit Aria, I weigh less on the Withings scale and my weight varies less from one weighing to another. But my body fat is lower on the Fitbit scale. Accuracy is certainly an issue, but it is best to assume that no scales are entirely precise and use them to simply follow a trend.
Which scale is right for you?
Choosing one of these scales depends on how you plan to use it.
You simply want to record your weight: Either scale is good enough to record your weight, at least to keep track of its trend. But if all you want to do is see your weight, save some money and get a scale that does not calculate body fat and does not sync via Wi-Fi. Good scales like this cost less than $25.
You are wedded to the Fitbit or Withings ecosystem: If you are already using a fitness tracker or other device made by one of these companies, then you are more likely to want the scale that works best with that device, and whose data shows up in the same app.
I am not a fan of the Withings app, and Fitbit's app offers more features, such as the ability to record the food you eat and calculate calories based on activity and meals. Withings, on the other hand, offers a wider range of devices, such as a blood pressure monitor, a sleep tracker, and more.
You want your weight recorded in Apple's Health app: If you use the Apple Health app on iOS--perhaps in conjunction with an Apple Watch--then the Fitbit scale is not for you. Fitbit's app doesn't sync with Apple's HealthKit, whereas Withings' does. So if using the Health app is essential, you will want to choose the Withings scale.
Remember, you can manually add readings from any scale to either the Fitbit, Withings, or Apple apps. The real advantage of these Wi-Fi scales is convenience; you are paying extra to save the step of manually entering data. If you are willing to spend more for that ease-of-use, then either of these scales works well.
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