I would say variety is best. The hikari foods you mentioned are good but also try the h20 wafers from NLS. Not sure if Omega has a good sinking pellet but I am sure they do. I feed my rays 5 different foods every day, I figure I should have my bases covered.
I am also a big advocate of having some non-pellet food in their diet including nightcrawlers or fresh seafood like smelt, tilapia, market shrimp etc.. just to mix it up and keep them interested