"Hank" Mule UV light options? Pros and Cons?

Perhaps my search skills are lacking regarding UV flashlights but, here I am …

Reddit gets mainly a “cut and paste” of the same content which is a good start but, sort of misses the target as well.

MULES” are a reasonably popular term but, I am wondering about my model options. The D4V2 seems to get almost 100% of the comments and reviews but, I’m wondering about other models like the K9.3 and KR4 along with battery options (18650/26650).

I also prefer tail switches so, I don’t know if that is even an option or what effects it might have on performance. I should also note I am looking for more of a flood and not a thrower (~20 yards is plenty for automotive, scorpions spotting and, household uses).

Any KR4 UV owners have one to comment on versus other options?