Whenever you have aficionados you have snobbery. It’s inevitable. Artisan bread baking aficionados are snobby about their leavening. They think natural leavening (sourdough) is the shit. Bakers yeast is not.
Bakers yeast is what most people bake with. It’s the stuff you find in the baking aisle at the grocery store. Most people use the dried kind, which either comes in packets or small jars. The yeast looks like tiny-tiny tan twigs. You can also sometimes find little cakes of yeast in the refrigerated section. They usually come in one ounce cubes.
This yeast is domesticated. Domestication is what we do to genetically modify our food, and we’ve been doing it for thousands of years.
Take dogs. We can breed dogs to look a certain way. If we're looking at a group of, say, Cockerspaniels, we might decide that we like the ones with longer hair. And if we want the next litter of puppies to have longer hair, we pick a long haired male and longhaired female to breed. It’s more likely that the litter from this couple will have longer hair than the litter from two shorter haired spaniels. Inheritance. Genes. DNA.
We’ve been intentionally doing this with plants for more than ten thousand years. Wheat was just a prairie grass that looked nothing like today’s domesticated grain. We've coaxed bitter, meager wild fruit into the buxom market variety we eat today. By picking and planting the individuals we like, nature has obliged and given us protein rich grains, sweet fruits, and starchy vegetables.
Bakers domesticated yeast by selecting for a strain that eats quickly and farts a lot. (Brewers have done the same thing to get lots of alcohol out of their yeast.) When you catch yeast out of the air and first start using it in your sourdough recipes, you have to wait a long time for it to inflate your bread.
Typically when you make bread, you mix your dough, knead it, and let it sit for a while before you form the loaf. While it sits, it inflates to about twice its original size. With your recently captured wild yeast, this will take maybe 4 to 6 hours, or longer. With bakers yeast, and a warm temperature, it'll take as little as 30 minutes. Obviously this makes things a lot easier, since bakers' yeast speeds up the process and has a fairly consistent rate.
So why use natural leavening? For one thing, you get a more interesting pattern of bubbles in the dough. And by "interesting", artisan bakers mean non-uniform bubbles. They really like big bubbles. Cut a good sourdough loaf in half and you should get a few huge holes, some medium sized ones, as well as the more uniform smaller holes. Bakers yeast will give you pretty much just uniform smaller holes.
Another thing is the taste. Sour dough is a bit sour, though it shouldn't be overwhelmingly so. Sometimes it's described as tangy and maybe a bit "nuttier" than breads made with bakers' yeast. But as a sourdough starter matures, it becomes less tangy and tart. It shouldn't really be all that sour, but the taste is distinct.
Sourdough also gives a thicker, crispier crust to breads. If you're into that.
I end up using bakers' yeast much more often than natural leavening, just because I don't always have 6 to 10 hours to baby-sit a slowly bloating lump of dough. But when I have the time, it's worth it.