I have three scales at home and one at the gym, all four give me a different weight. That's because they are instruments as any other instrument are calibrated over a measure.
Choose one and stick with it. The new or the old doesn't change a thing, it's not the 0.6lbs that will make a difference in the long run. A big glass of water could weight enough to make you weight 0.6lbs more, don't make a trouble of it, it's not. Just choose one.