Same flour, same ingredients, same process -- except; left - a yeast preferment [poolish]; right - a sourdough preferment -- very different breads in external appearance, crumb structure and chewiness, and flavour.
Production line baking at work; some undisclosed experimental breads as sandwich breads. had a little problem with the scaling for the breads at the back in the second jpg; a problem with the baker, not a problem with the flour .Nice crumb for hand molded.

Same day; a nice part-wholewheat sourdough batard; very flavorful, thin crust, and chewy crumb