Like way more accessible PAR reaching the actual plant leaves. Do ur research on ppfd photosynthetic photon flux density and DLI daily light integral because these numbers are the numbers that matter to the plant and to ur yeild. I.e. The total usable light (400 -700 nm which is the correct wavelengths to best support photosynthesis ) the plants receive per square meter per second over the course of the entire light cycle . Compare usable par after inverse square law for both configurations led and hid, bare in mind ur going to calculate the ppfd and DLI not Lumens or light intensity ok. figure what ppfd and DLI u r getting from ur hids and honestly do the math and see for yourself which light is truly more efficient. Remember people leds produce hardly any heat and we all love our co2 but don't forget to raise your thermos up or your plants will have that larf effect ( stringy ect. ) If u do not supplement co2 run a colder room with LEDs and your yield will increase. I have been doing this for only a few years so plz I'll take all and any advice or extra insight thx everyone.