ABSOLUTELY the round. Ppl SWEAR by the square b/c they don't want to waste bread....square mold, square bread...makes sense. But they don't make bread big enough to FULLY cover the square mold....so they don't seal nicely. With the round, the bread covers the whole mold and seals very nicely. Sure, you have to cut off the very crust of it, but I'd rather have nice sealing than not waste bread.
You should see me when I buy "pie mold bread." Nothing can touch it in the cart. I'm a crazy woman at the check out making sure no one manhandles it or puts it in a bag with something that will squish it. I bring it in the house very very carefully---like I'm carrying a fragile crystal or something. I don't like ANYTHING to squish my pie mold bread.
Hey, we all have our priorites.