you should use both I am using 2 t5's and I am struggling with the lower sections of the plant getting light my plants are about 3.5ft tall and having to keep the them @3in away from the bulbs(heat) is sucking I wish i had a HPS. I would recoment you put the HPS 2ft above the plants and rig the T5s too either side of plants to get more light too middle and lower sections of plant, got some pics?