ChrisB, the 6500K T5's can't really be compared to the Blue Plus, one is a yellow/white light and the other is blue.
The 6500 will be brighter, but a very different color spectrum.
Typically, from my understanding, the lower range bulbs (6500, 10000k) are brighter at the same watts as the more blue bulbs (14k, 20000k, actinics).