Got my H600FCs in today!
All 3 are pretty indistinguishable in terms of anodizing finish.
Lenses seem to be all equally frosted.
Tint difference between the three is very minimal. The camera has a hard time picking it up in this case, but the one in the middle is ever so slightly less rosy/more green than the two on the outside. Deciding between the other two was very hard for me. I ultimately went for the one on the right.
H600FC MK4 on left (93-95cri XHP50.2 4000k), SC600MK3 HI in middle (80cri XHP35 HI 4500k), H600FD MK3 on right (83-85cri XML2 5000k).
The tint differences here are slightly exaggerated. In person I saw the HI's hotspot to be slightly less greenish than it is in picture, but only a little bit. Also keep in mind that my particular SC600 MK3 HI was also cherrypicked between 3 different samples to be the least green I could get it. The differences in tint between the three samples for those was more apparent than the 3 samples of the H600FC I received today.
H600FC MK4 on left, H600FD MK3 on right. This picture is fairly accurate to what I saw in person at the time with my currently adapted eyes. The tint on both is pretty great, but I would probably choose the FC for nighttime tasks, not to mention its higher output and higher CRI (which will be much more subtle of an effect than just discerning the raw differences in color temperature and how that affects spectral balance on objects you view.)
A couple of observations: Zebralight says you can use a protected 18650 for the H600FC's highest output, but it needs be capable of highish drain regardless. The Olight 3600mah 10amp battery I put in it refused to work with the H1 output. A keeppower 3500mah did work, however. For the sake of reduced resistance, I would run unprotected cells only in this light.
The luminous efficacy of the XHP50.2 is great. The H2 output of the H600FC MK4 (980 lumens) takes way longer to get hot to the touch than the H1 output (870 lumens) on the H600FD MK3, even though it's rated for a higher CRI. An advancement of 2-3 generations of LED tech.
I will do some runtime tests next.