I say that whatever u measure in because so many companies advertise in different ways as far as efficiency. Efficacy however u want to look at it lol. I look at what the light does period and how much it takes to do that. I like ppfd charts. For someone who doesn’t really look they can be deceiving a company I was just looking at advertises flowering under their light is 5x5 area but show a pot chart for a 3x3 area and a 4x4 area and in a tent. The numbers outside the tent in the 3x3 area were so weak anything outside that area like the 5x5 they advertised will basically get nothing. Boy that website made it seem like a solid 5x5 flowering light and veg 7x7 but I can’t see it doing much outside the 3x3. I know u want info and should get it as soon as Sm0 pops in.