Do I really need a Dutch oven if I have a stockpot?
If you mostly boil pasta and make broths, a stockpot is fine. But a Dutch oven sears, braises, bakes bread, and holds heat the way a stockpot can't. If you make soup more than twice a month, it pays for itself in dinners.
Enameled vs bare cast iron. Which is better?
Enameled is more forgiving (acid-safe, no seasoning, easier to clean) and a little prettier. Bare cast iron is cheaper, lasts forever, and develops character. There's no wrong answer; I own one of each.
Is the brand worth it?
For Le Creuset and Staub, yes. The build quality and resale value are real. For everything else, look at the spec, not the logo. The Lodge enameled options are 80% of the quality at 25% of the price.
What about cleaning a stained interior?
Half a tablespoon of Bar Keepers Friend, a wet sponge, two minutes. The cream interior comes back almost new every time.