Like Bob said, it comes down to the reflector.
On a lumen per watts basis, today T5 NO bulbs are the most efficient lamps available (that are useful for planted tanks). So from that point of view, not worth it isn't the right answer.
For a high light tank, it makes more sense to go with HO bulbs. Also, there is a better selection available.
For a low-light or not too deep medium light tank, T5 NO would be an excellent choice, better than the fatter ones.
Big Als and Commodityaxis sell a good variety of NO T5's.
In your case, since you want to grow high-light plants, HO T5 would probably be a better choice.