In my opinion, no natural fabric is as comfortable as synthetics. But I have cotton bedding and curtains. I think these are higher priority: bedding is used while you're lying close to it and easily able to inhale any dust, and curtains are exposed to sunlight that can weaken the fabric and make it break down more easily. They're also both large, meaning there's more plastic to be released. Carpet also seems a high priority, although that's more expensive and difficult to change.