Fast answer: Not necessarily.
Long answer: To the uninformed buyer, you might think that buying a duvet with more down in it must be better than one that has less. Kind of like, buying groceries at the grocery store...more must be better. Right? Wrong.
When it comes to buying a down duvet the factor that changes everything is the loft of the down. Technically speaking, if you use down that has more loft to it you would need less of it to get the same result.
But when you look at duvets at a department store, they always talk about the ounces in the duvet. They perpetuate the myth that more is better. But the trick that most down duvet manufacturers use is that they add feathers to the duvet to add weight to it. But feathers aren't insulators. They are cheap and you can add a bunch of them to the duvet, market it as having "more" so the buyer thinks they are getting a deal when in fact they are getting fleeced.
We only fill our duvets with down fibers. While you can't guarantee that they don't have some small feathers in them, it's not our policy to add weight to a duvet with stuff that's not good for you unlike the department store duvets.
When you have a duvet filled with high quality down, many of our clients are surprised by how light they really are, and just how warm they can be.