Richwouldnt, I don’t think they’ve been directly compared, but I did at least volunteer to review the CU6 and compare it to other lights a while back. I didn’t get approved though.
As for the KD drop-in vs CU6, the CU6 is spec’d at 3W of power in UV mode, while the KD drop-in runs either lower or higher depending on the number of cells used. I got it running as high as 5W or as low as 1.5W, from what I recall. 600mA at 8.4V is what mine does on two cells.
From the sound of things, either of the LEDs djozz reviewed recently would probably out-perform both the CU6 and the KD drop-in:
I’m kind of tempted to make a 1x16340 UV light with a really nice Ledengin XP-G sized emitter… but it’s a very very low priority since this P60 works more than well enough for my purposes.