T5 lights are more efficient in converting watts to light intensity, so the same wattage T5 fixture will produce more light than the AHSupply light. This is assuming you use separate reflectors for each bulb, as most good T5 fixtures do.
I proved this to my satisfaction by visiting a LFS that had tanks set up and lighted with T5, HQI and AHS type PC bulbs. I could look at the PC bulbs with little discomfort, but not the T5 bulbs, and not even close with the HQI bulbs. Real science at work!!
I am looking at a similar situation. I am setting up a 45 tall (20 long/29 gallon footprint, just really tall) and I am trying to decide between 48 watts (2x24w) of t5 or 2x55watt bright kits. I know that t5s with good reflectors are better per watt, but are they more than twice as good? That's what it would take to overcome the shear wattage that the PCs bring to the table. Since my tank is only 30" long, the options are limited. Any insights? Hoppy? Others?