I consider ultralight as getting it done with a high degree of discomfort. I think lightweight adds enough comfort in a very managed way to make a light load more enjoyable ie ltwt tent vs tarp, a little extra food and indulgences, a full toothbrush instead of one with the handle cut off, etc. I also think ultra light can be closer to dangerous depending on terrain/weather/season. Ultralight seems to work better closer to summer, whereas lightweight is more important the colder/wetter the weather.
