T-5 Bulbs last much longer
they run considerably cooler than PC (you won't burn yourself like you can on PC)
and with the right reflectors they actually put out more light than a PC. Flat reflectors don't do much with T-5 lights, but Sunlight Supply and IceCap both make reflectors designed to take advantage of the T-5 design and get morelight into the tank. The Sunlight Supply reflector is ( M ) shaped, this allows the light shining straight up to be reflected around the bulb and into the tank. A flat reflector will just reflect that light back into the bulb.