8

Your question is a bit of a can of worms to answer because I think there are a few basics that need to be addressed first. I’ll let other people do that, but I just wanted to point out that both the D4 and D4S are very, very much hotrod flashlights. People talk about them because they are cool designs and made well, not necessarily because they are the best at “being a flashlight,” something that means different things to different people. Motorcycle enthusiasts talk a lot about fast Ducattis and big, loud Harleys — not so much about their mid size, metric cruisers that they actually own and ride every day. I can use my D4 to start fires (dark pieces of paper placed right in front of the lens), to illuminate entire fields at night or to output a variable brightness just bright enough for what I need, including so dim that my eyes can preserve their night vision. Notice how I mentioned the two least practical uses first? It’s just that kind of flashlight, they both are. If I use a D4 for more than 20-30 seconds on max brightness, it becomes too hot to hold bare-handed and the temperature regulator ramps the output way down to about 15% brightness, which is extremely dim by comparison. The D4S is different mainly in that the optic gives it more throw and less flood (but it’s still plenty floody outdoors), and it can go for longer on max brightness before becoming too hot to hold or too dim to be useful, but it does eventually become too hot to hold barehanded and gets considerably dimmer if left on max for several minutes.

1) D4 has more flood
2) Each emitter has different characteristics in terms of throwiness, the perceived tint of white light and how “true to life” it renders colors (i.e., the CRI).
3) Totally up to you.