Let's define our terms a bit. What has become called, generically, "night sights" are sights that have little phosphorous-lined vials of tritium installed in them. These glow constantly, due to the radioactive tritium causing the phosphorous to glow. Trijicon is a maker of such sights...as are Meprolight, Heinie, Wilson, Novak, P-T, and others.
The fiber-optic sights collect ambient light via a piece of fiber-optic "light pipe" and make the end of that pipe appear to glow brightly to the shooter. If there is no ambient light, they do not glow. SDM Fabricating, EGW, Brazos, Williams, and a number of other firms offer these.
The "True-Glo" sight (if I recall correctly) is a fiber-optic type sight with a tritium vial inserted in the "light pipe". This would seem to offer the advantages of both styles.
So, at high noon on a sunny day, the fiber-optic sight will appear to glow the brightest and the tritium night sights will not even be noticeable. In a dark warehouse, the tritium night-sights will be highly visible, but the fiber-optic sight won't be glowing at all. The "True-Glo" (if my recollections of how this sight is made are correct), would be highly visible in both environments.