I use Nature's Best all flock. The nutrient analysis is comparable to Purina organic starter/grower, but has higher protein. My girls seem to like it more than the Purina (they were in two different feeders at one point), and I haven't had any health issues.
I think that is the key point. What is the guaranteed analysis and the age of the feed.
Another thing to consider are the nutrient levels of micronutrients that aren't required to be on that analysis tag.
The only things required to be on the guaranteed analysis tag are :
Crude Protein (min).....................................................
Lysine (min)..................................................................... Methionine (min).........................................................
Crude fat (min)...............................................................
Crude fiber (max)...........................................................
Calcium (min)................................................................
Calcium (max)................................................................. Phosphorus (min)...........................................................
Salt (min).....................................................................
Salt (max).....................................................................
Other nutrients are known by the manufacturer from the assay done with each production run. They just don't have to report them. In my experience if you want to know the level of any other nutrient, a phone call to the producer will yield the answer.
IMO, if other nutrients are listed, like vitamins A, D or E or a mineral like selenium, the producer is advertising that information out of the kindness of their heart, and it tells me they are proud and confident of their feed.