I have no personal experience but after looking at the company's website:
either one will probably work.
The higher protein is probably better for growing birds and for layers, so if possible I would go with the 20% rather than the 16%.
The layers need more calcium than that food provides, so I...
Correct spelling for a young male chicken: cockerel (I think of it as cock-er-el when I need to spell it.)
Spell check is hopeless with words that are spelled "correctly" but are not the word you want, which can be very frustrating sometimes!
There seems to be a common misconception that chick starter and all-flock feed have no calcium. That is false.
All chickens need some calcium. All complete chicken feeds contain some calcium.
Layers need more calcium than non-layers, so layer feed has the higher level of calcium.
Chick starter...