I think if you started weighing yourself on one scale, you should stick with that scale.. for consistency. Just pick a scale and stick with it.
If you want the most accurate version of your weight, head down to the doctor's office (or even a gym, a community center, some place like that) and ask them if they will weigh you
Then you'll know which scale is closer to the truth.
But no matter what the ultimate number is.. you aren't 6 lbs heavier than you were yesterday! It's not necessarily about being one weight or the other.. it's how many pounds you've lost, and the only way to track that would be to use the original scale (or adjust everything by 6 lbs for the new scale).
Home scales can be dicey, I just bought a new digital scale which puts me an entire pound less than my old digital scale, urgh.
That may sound like a good thing, but I'd rather have consistency and be a pound "heavier" (I'm not any heavier, but you know what I mean) than deal with the change!