Hank doesn’t offer XP-L HD in the D4, so I am going to run with XP-L HI. Because Firelight2 was talking about being able to run his Zebralight for a significant amount of time at 1000 lumens let me do some comparisons.
Texas Ace tested a XHP70.2 that was 80 CRI. I can’t find any tests for the 90 CRI version, so I am going to run with his test. At 1319 lumens it used 6.9w which is 190.3 lumen/watt. He did state in his tests between a low CRI version and 80 CRI there was little difference at lower power and 8% difference at high power. I think that makes sense because of the lower Vf.
Texas Ace also tested a XP-L HI 1A V2 which is 70 CRI. At 327 lumens it used 2.2w which is 145.4 lumen/watt. So if you had 4 in parallel it would be around 1308 lumens using 8.8w. Obviously many other variables come into play and this isn’t a completely fair comparison. Those numbers suggest up to around a 30% difference. But if there was only a 10-15% efficiency gain if you stack that with a much more efficient driver then it really adds up.
I personally can not stand the XHP70.2. I use my flashlights inside mainly, and I am one of the worst white wall hunters.