Apple butter vs apple sauce in a bbq sauce recipe?

I would use the apple butter, without any additional sweetener - but perhaps might adjust the sweetness with a touch of honey after tasting it.

You might find as well, given that apple butter is usually thicker than apple butter, that you need to add a touch of liquid to achieve the right consistency. I'd add extra vinegar in that case, but you could also use more wine, or even water. ;o)