It seems like single crochet in the back loop, reversing direction each row, would create the same fabric as single crochet in the front loop one row, and single crochet in the back loop the next row in the round. It does not.
In the photo above, the left brim has some ridges, but feels thin. The brim on the right is soft and squishy.
The single crochet in the back loop switching directions is vastly superior as a hat brim and honestly for any other application where warmth and comfort is needed.
Interesting.
Critters and Craft 