the change is really in the ballast. The ballast which powers the light, give the light more power, allowing the lights to "pack more punch". Individual reflectors just increase the amount of light going into the tank. With the combination of these two items, you have one heck of a lighting system.
The T-5NO (normal output) will grow most mushrooms, polyps, zoas. Basically softies that are high up in the tank. The T-5HO (high output) is with the additions of the above said material.