Both if you have the equipment. Having some of measurement capability combined with your senses, can't be all bad.
PICOGRAV's Vero29 grow pops into my mind. Lie's? Quite the opposite, the HID killer. There is a reason dinosaurs are from the past.
And you are using an example "UFO" which has no statistical correlation. There are so many knock-off's and variations of that light, literally the 1st "commercial" mass produced led fixture. But that was 5 years ago, lol, where yah been?