I love how I always have to back up my claims but no one else does. Then we got this dude who has not even used LEDs arguing. LED is junk, if you can't control heat you have improper ventilation. How's this? I have REAL WORLD experience with t5's, HID, and LED's. For the price of the led lights you could buy a small HID and all the fan's, ect you need.
So how does a so called 'pro' grower examine lighting?
Efficiency vs Cost
Led's are by far the wost, reduced yield and high cost.
T5's are the 'middle' ground reduced yeild, poor penetration, higher cost per watt than HID
Now the winner is HID. Why? A 400w HPS puts out more light with greater penetration than an 8 tube t5. If the bulb is exposed it puts off less heat as well. Want to know the kicker? It uses less wattage than the 8tube!
So what are t5's and LED's for?
Growing at home in a really small space (a closet can easily accommodate a 400w hps). They are also a marketing ploy, this stuff is VERY cheap to manufacture. You just pay the 'gimmick' tax.
You are more than welcome to spend thousands on LED's while skimping on other equally important factors in grow space design. Not me though