New Life spectrum is supposed to be the best ingredient-wise. No preservatives like ethyoxquin which is said to cause cancer, good whole proteins, not much filler.
I have fed my CA's a mix of NLS, hikari gold or bio-gold, southern delight, and omega one pellets over the years. Probably more I can't remember. I honestly don't see a huge difference in the fish's health or color from one food to another. I usually go with NLS as a default, unless the fish prefer another food, then I give them the other one. I mix in some frozen meaty food as treats as well.