HID customers can go by true Watts, its simple, 1w =1w and I want 40W+ per sq ft. Done deal.
The LED manufacturers make it more complex with a whole new set of acronyms, and 95% of them flat out lie about the coverage. They will claim to cover a 4 x 4 area for flower but if the PPFD map goes below 600 in the corners, they are lying and what's worse is they know they are lying. Buds need 600 PPFD min in flower. Those buds in the middle that are getting 1100+ PPFD are doing great but they dont share the PPFD with the buds in the outer corners so the average means nothing.
i run 2 or 3 1000 watt HIDS and I would love to replace them with LED's because of the electrical costs of powering them, and the added costs of the AC to cool the grow room.
All that said, pick a light and grow something, what ever you pick will be out dated and on sale someplace by the time time is arrives so just take the plunge.