I experimented with different headlight lenses. I have pre67 front fenders. I removed the glass from the H4 and tested different headlight lenses, so my tests might apply to your question.
When testing different lenses with the bare H4 housing, I notice the fluted lense gives a wider and more evenly distributed light pattern than the clear lens. I judged this by looking at the light pattern on a flat surface about 3' from the light. The clear lens gave an intense center with a narrow distribution while the fluted lens gave a diffuse, but larger distribution. I went with the fluted lens (with the H4 housing lens removed) partly for the looks of the lens (911), but also because it seemed like a diffuse output would light the road more evenly.
The "clear" or diamondback H4 may look better/different, but I'm not sure the light output/distribution is better. The diamondback facets may project the light better than the flutes do, or the Bosch H4's with fluted glass may turn out to be the best for light quality (intensity and distribution). I've got an extra Bosch H4 unit if you want it (as long as you post your test results
). Then you could buy a clear/diamondback unit, test them side-by-side, and buy a second unit of the winner.