The T-5 4 bulb fixture cost more ,bulbs cost more and are hard to find or order from E-bay . T-8's and 12's are common and cost less and like Toka said the T-8 put's out as much. I think the T-5 might make more heat. Not sure . The 4 bulb set up will vegg a 4x4 area nicely. You will hardly notice the 4 bulb set up in your bill. 28 - 32 watts a bulb .