LEDs - Well, this is interesting

[Ron99]

Kessil's have UV but barely. Around 390nm or 385nm IIRC. So in my opinion it's more a marketing thing than a real "UV" advantage. What might make the Kessil work well is the amount of light being put out around that range rather than the actual; wavelength. i think the Kessil has more violet than some other fixtures. One outputting the same amount of light at 405 or 410 might well perform just as well.