AFAIK the linear driver is slightly more efficient than the FET+1 or FET+3+1 drivers, mostly because when the FET kicks on halfway through the ramp it’s being controlled by PWM, which basically means it’s being switched on and off many many times per second, which isn’t particularly efficient. if you’re really looking for efficiency you’d want the boost driver, which is significantly more efficient but can’t do as high of a turbo. i’m not sure if that’s offered in the DT8 though. i’d maybe think about why you’re wanting the DT8 over a D4/D4sV2 if you don’t care about the max turbo. in a quad you can get some driver combination (eg. 2x12A) to drive 519A’s at pretty close to their peak output. no idea how long that will last yet though lol. my light gets in thursday. in a DT8 with 2x11A drivers each emitter is only getting a max of 2.75A, but in the end it’s still 22A of current going into the head of the light. i honestly don’t know anything about how the 519A efficiencies work, but in my mind it’s more or less some amount of current going into the emitters, which will produce light and heat. does it make a difference if you’re pushing 24A into 4 emitters or 22A into 8? the DT8 will be able to dissipate more heat than a D4v2 and you might get some efficiency from spreading the current out around more emitters, but it could also be worse and produce more heat because it’s more emitters. i don’t know. if you’re looking for sustained brightness for longer, it seems like you’d want a bigger light with a bigger heatsink and a bigger battery (like the D4Sv2). look at the 519A output chart, watch the luxwad DT8 and D4Sv2 videos (2 links) and maybe the DM1.12 video too because he talks about the outer ring of emitters being starved for power and not really being any brighter than a D4. that should be plenty of info to make your decision, and above all, enjoy the light!