Before a couple of years ago I would have said either or both (Omega One and NLS) based on years of side by side comparison-- though I would have told you some Omega One products were better than others. I would also have said which one makes fish look better sometimes depends on species, a few of my fish would look better on one or the other, but mostly little difference. Growth, health, etc. was excellent either way. The occasional complaint with NLS is dust or tiny particles in the water from the pellets; it seems to vary, some containers I get it, others not. My impression/experience is some of their products are more prone to this than others, I've yet to see it in Ultra Red or Algae Max, for example.
All that was before Omega One changed their formula a couple of years ago to include a bit more of the cheaper ingredients. Since then I've stuck with NLS (tried Northfin's version of bug bites at one point and I wasn't impressed, haven't tried their other products)