I also got the cognac instead of the black, because I like the look better with dark denim. I also wanted something that would contrast with my black dresses. If I wear black dress + black tights + black boots, it's too much black. So I think that the boots will relate beautifully to the denim, and will be versatile if you wear a lot of black in general. I wouldn't worry about the topper. Either coat will work.
But, I'm not sure about pairing the boots with a black bag. Something about that combo seems to clash for me. I guess it depends on the entire outfit. Do you have a cream bag? Or olive green as GG suggests? Or something in a brown tone that "goes" but doesn't match the boots?