the ST-76 is a really tough treble - I haven't seen one opened up yet although Eric Le Guyader told me that he had one open up in New Caledonia earlier this year.
As Ivan said, the only thing is it is very heavy.
ST-66s works fine unless you are targeting really big fish. Also, the 66 comes in barbless whereas the 76 does not. I grind them off with a dremel anyway