when it comes to lighting.. t5 vs t12?? HELP

can anyone tell me what the differences/benefits are to having a T5 fixture vs a T12 fixture? or is there even a benefit of one versus the other? help plz

T5's are high intensity flourescents (more lumens), T12's are what you have around the house.

T5 HO is the most powerful available. The only tube grow lights worth using IMHO.

sweet.. thanks for the help. The people at lowes have no clue what they are talking about!!