Here was my reasoning for black out/white in.
I liked the look of the letters, but have seen way too many wheelers with the sidewalls torn up pretty good. And all that white lettering not only takes a beating, but the whole sidewall is white underneath the layer of black (it's how they get the raised white letters with black borders) and it looks like doo-doo.
Now, if it rarely sees hard rocks or sharp objects, then by all means go with white out if that's the way you like the look. But if you plan to use it in thick brush or rocks, I'd go black out.
Paul