Brightness is the highest with the XP-L HD.
However, for best usability in all conditions, the SST-20 5000k would be your best choice.
Is it noticable difference? How many lumens? I guess SST is more focused, giving this light a little more throw?
The difference in lumens is not noticeable.
And it is more focused, and does give a bit more throw, making it more usable at lower power.
Thanks! 
Yeah, I agree.
4000k is my choice though.
I don’t know how the other leds performs and what type of beam they have.
But the SST20 has a really good all around beam i would say. I love mine.
If you unscrew tailcap for a sec and then turn the light on, it will come on in the highest 3x7135 right? and this is the most efficient mode for the amount of lumen you’re getting. My question is why is that? why if you bump it a little higer it gets less efficient?
Because the FET is direct drive and is regulated through PWM, if you are beyond the max level of the regulated 7135 chip then you are engaging the FET and this means you have the full amperage involved only it’s pulsed. Thereby, less efficient. 
I really like this light.
ow oke I get it now. Thanks. Is that a reason people dont like cheaper lights with pwm for modes instead of regulated? and also flickerg in low modes right…
On some older or cheaper lights, PWM was slow and visible and unpleasantly like using a strobe light. Also, it tends to be less efficient than a true constant current circuit.
But on newer lights with faster PWM and multiple power channels, the visual difference is beyond human ability to perceive without tools, and the efficiency difference is relatively small. So there haven’t been a lot of complaints about it lately, except from people who are still thinking of the older models which weren’t very good. And a few who really, really care about efficiency or sophistication.
Annnd, most of the cheaper lights also have the blinkies on the main menu, no way to run through the modes without encountering Strobe, SOS, and Beacon. That gets really old really quick.
I just ordered a D4S with an SST20/5000K emitter. I have several fresh 26650 batteries at home to chose from.
What performance differences might I expect from these batteries? (No brand names below, just their advertised specifications):
Is their any risk to the emitter or driver if I use #1?
Will #3 provide enough amperage to realize the advertised output of the D4S/SST20 ?
1) 4,350Mah; Unprotected; Hybrid IMR; Max. Discharge current: 47A (5 Sec. ON /30 Sec. OFF);
Max. Continuous Discharge current: 36A (With cut off at 80C).
2) 5,250Mah; Protected*; Hybrid IMR; Max. Constant Current Discharge 15A (Protection circuit - cut off at 15A). *Note: This battery might be too long to fit: 69mm.
3) 5,750Mah; Unprotected; Hybrid IMR; Max. Discharge current: 30A (5 Sec. ON /30 Sec. OFF)
Max. Continuous Discharge current: 22A (With cut off at 80C).
Thanks in advance for your guidance.
The brand names are pretty critical for your question, just stating the printed capacity doesn’t give us any idea if the cell can actually meet the printing on the label.
Number 3 probably won’t deliver the specced output, difficult to say, again, without knowing who made the cell. Number 2 probably won’t either. Protected cells rarely do well with FET drivers. So it would look like, on the face of it, your number 1 cell will be the best performing. Blind guesswork of course.
So many tests of cells in net, just look for it, many people check cells. How is your emitter colour? I just ordered the same.
DB: Based on your thoughts, I will use the #1 cell.
Apologies. I would have given the brands, but they are all rewraps - all Orbtronics. Orbtronic, to its credit, seems to rewrap only quality, proven cells. Sol, the owner, makes his living on that reputation and his personal, knowledgable service. All the cells I have purchased from him have met or exceeded the specs I can measure. (I buy from him because the other reputable U.S. vendors won’t ship to Alaska. He gets the cells to me in 3 days - and from Florida no less. Costs more, but that’s part of living in Alaska.)
Kajman - I have not received the D4S SST20/5,000K yet. Should arrive in 2 weeks. When is does I will try to post some beam shots - comparing it to my D4S XP-L HI V2 3A (also 5000K). I bought this additional one hoping for a bit more throw distance
Exactly same reason, I have D4 and there is lack of distance at lower power.
I have been thinking about Sofirn BLF SP36 (blf q8 mini) too (additional to d4s) but I wonder if it is not really almost the same to D4S…. And as most of us I have too many similiar lights
My d4s sst20 5000k will be here soon. I wonder how it compares beam wise with the blf q8.
I guess Q8 will have more throw.
Yet another package from Hank arrived today; my third D4S - this time a grey one with sst20 3000K and amber aux. 
Also got a replacement aux board to fix the one with dead leds.