It’s a good question Don and I notice more even growth with staggered planting, and easier picking say of outer leaves from salads, since one can work all around each plant.
As you say though, for alliums there is not much difference, and I plant garlic in rows across beds, making it easier to hoe between.
On the other hand, I do not have many weeds!
Main thing is to keep asking these questions and notice the growth at say different spacings, to help find the answers that work best for you.
