I'm not in the US

so DOT certification is not an issue - in fact - as far as vehicle lighting goes, our laws are so primitive that they are ludicrous...
At the front we are required to have "a white light, visible at a reasonable distance" and at the rear, if the vehicle is less than 7 feet wide, "a red light, affixed to the right of center", we are also allowed amber "trafficators" and all other colors are illegal, so the cops will get you on bluish HIDs.
As for the Ultras vs the regular SilverStars, I haven't compared them on the same vehicle, but I'd say they're visibly brighter & whiter and probably better distance - Sylvania has a comparison chart on their website with percentage improvements that's I suspect is fairly accurate.
The vehicle with the regular Silverstars probably sees the most evening use, but not that much long distance, I don't see myself upgrading to the Ultras unless I have a lamp failure.