After talking with several low iron glass manufacturers, I have verified that it is in fact a myth that starphire or low iron glass is weaker and scratches easier than regular glass. Just thought I would share.
I have been making aquariums as a hobbyist since the 80's and have used low iron glass a few times. My last aquarium, a 120, I replaced the front pane with "starphire". I found it to scratch easily.
Your not going to see a difference in clarity unless you are a glass pro or have regular glass next to low iron glass.
Starphire is just a brand name. It is also called Crystal Glass and UltraWhite glass.
Is Low Iron glass worth the money? Yes IMO.
Is it worth the money for aquariums under 100 gallons? Not IMO.
Actually, I like the look of regular glass on tanks that are built out of 1/2" glass. It is easier on the eye because the iron filters out the glaring brightness from all the light you are pumping into a reef.