T-5's
T-5's are the way to go IMHO. There output depends on the ballast used and reflector that is used. On the Ballast issue, The Best is the IC 660 which will overdrive the bulbs to ~80-85w each. You still get about 2 yrs life out of the bulb. The next best ballast is the Triad by Universal Ballast, this is the ballast that Sunlight Supply uses. Drives the bulbs at the proper wattage, good life out of the bulbs. The third most used ballast is the Workhorse, which overdrives the bulb, but hurts the life of the bulbs, replace about ~9 months.
The Best combination is the 4 bulb IceCap 660, with the IceCap SLR T-5 reflectors.
You will have about the same amount of light out of that set-up as the TekLight 6 bulb unit.
They outproduce both VHO's and PC's as while using less wattage, and less heat.
A good reflector is a must, I like IceCap's, with the SLS's coming in very close behind.
Hope this helps.