It the initial lumen out put of a HO T5 that makes them so appealing. Approx 5000 Lu per bulb.
High Output T5
20% more light intensity then comparable fluorescent grow lights. No frequency filtering. No noise. Rapid start. They simply consume more electricity than their non-high output counterparts.
I currently run Quantum Triphosphor Lamps @ Grow (blue) Bulb - 93.5 Lumen / per Watt for 6500 Kelvin.
They are a little pricey but I really like them. They are time tested and proven themselves to me.