The 2X10 watt CFL's
are certainly brighter both because they total 5 more watts and they are basically a T5 type bulb. (BTW, my tank has a glass canopy as well.) I can't grow most carpet grasses in this tank but the Helanthium tenellum (right foreground) does well with that amount of light. If you go with the T8 I would recommend adding the LED strip if it is in the 6500K spectrum you need for plant growth.