I have to say that there are no "black eyes", just dark brown eyes accentuated by various tones of skin to look like they are black. And sine you didn't have a deep research or let me say the observation on the so called black eyes, actually, and then are not black at all. The difference can be subtle or distinctive depending on the eye-colour. "Brown" can range from light, pale brown to deep, dark brown, which can be easily mistaken for black. Examples would be Asian. Asian have typically very dark brown eyes. Just go with your instincts. There is no officially correct answer as to which colour people's eyes are.
And if you want have the real dark eyes, you can were contact lenses with the color of dark. That is pure dark, and by the way, you can compare it to the natural so called black eyes, then you can see the difference by yourself.
Well, as you can see, people of different races will have different colored eyes. However, the differences between them other than color are simply not obvious. And that is the reason why people of different races are equal in terms of every criteria. Maybe with the development of science, we will have more answers. Anyway, maybe their sensitivity to lights is different.
There will be no big difference between the black eyes and brown eyes except the different eyeball's colors. The difference is so subtle because it is defined from the genetic endowment. You could change the original color of the eyes by wearing the colored contact lenses. However, the brown eyes are more attractive than the black ones.