well i quess if ya dont have the extra power the t8 would be brighter then the t 12kickeralpine said:t8 will put out more light and run cooler then the t5. t12 would be brighter then the t8 but takes more power to run it this is just what iv read. the bigger the tube the more light ya get but it takes more power to run these bigger tubes so best all around buld would be the t8 .