Do we only have access to one? or do many people have them?
The Mata Masks would be good for individuals, but not really for the world. If there was only one, the use wouldn't greatly impact Earth on a global scale. If everybody had them, there would probably be crime spikes owing to the Kakama and Pakari, and privacy invasions owing to the Akaku.
The Kanohi Rode (Mask of Truth) would definitely revolutionize the world's justice organs, and the Kiril (mask of regeneration) would be helpful in rebuilding damaged towns and cities, though only if many people had them would it make a huge difference.
The Rau (Mask of Translation) would be extremely useful in archeological finds and re-discovering dead languages, and the Mask of Psychometry, which allows the user to see an object's past by holding it, would assist in the same field, though to a far greater extent.
A mask of Plantlife (Which does exist, though we haven't seen one) would aslo be useful in restoring the world's lost wilderness.