You can install our site as a web app on your iOS device by utilizing the Add to Home Screen feature in Safari. Please see this thread for more details on this.
Note: This feature may not be available in some browsers.
I did not order the black nor the obsidian black metallic. But from what i saw in the SC the regular black is darker than Obsidian black. But i could be wrong tho.
We looked at the 'original' black, and once we got to see the 'new' Obsidian black metallic before ordering my wife's S70D, we liked it much better. Metallic look--more interesting. It's a matter of taste. Go look....
My DS told me there was extra layer of paint/coat on Obsidiian and would likely be more resistent . Also the metallic look will cover up better if you get some stripes on it.
I love my solid black I don't see much difference - parked near by obsidian black Model S already and from a few feet I see no difference. Picture below of solid black