If you follow the tone threads here and elsewhere over time, you may find, as I have, a common issue is whether X versus Y changes your tone enough to be-1- noticeable; -2- worth it. It could be, as here, the nut material. It could be the fretboard wood; or the body top wood; or whether the bridge is brass, steel, aluminum, titanium. Or this versus this tube. Or you name it. And so forth.
Much of the time people will say, "Yes, I can clearly hear the difference." Sometimes, those people include you and me! But it's almost never based on blindly and simultaneously A-Bing the different components in any kind of scientific or controlled way. And it's very rarely based, when it comes to parts like nuts, on immediate-in-time comparisons where a person is likely to accurately remember what the prior tones were.
If you took two identical guitars, one with a brass nut and one with a plastic or bone one, got handed the guitars serially with a blindfold on in an ensemble setting, and heard a *significant* difference in tone, please describe further your experience. And also if you didn't test the two guitars blindfolded but you used some sort of *objective* measuring device like a frequency analyzer or an oscilliscope.
I beg everyone's pardon here for coming off (as I know I am) like such a killjoy but, for better or worse, I've become increasingly skeptical, over the years, on many of these "significant tone difference" arguments.
Now, after all this, what I, personally, hear, in a non-scientific way, with my own brass nut Tiger, is that open position chords seem to take on more of an acoustical-almost quality (that I'd never even think of describing as "heavier") relative to what I hear in my other guitars. But I couldn't prove that's due to the nut because I don't have another of the same guitar to compare the current one to, controlling for all other potentially relevant factors.
My last remark will seemingly contradict the prior but what the heck. Still ... everything affects everything!