i have never ran the T12's; but i do like the coverage and color i get out of the four giesman/ati bulbs i was running. Just a couple days ago, i think one of my T5 bulbs burned out ( haven't had time to trouble shoot yet). So i switched over to a 250w MH setup i already had. The color is much different, however, i see more shadows because of the MH. I miss the T5's