In this context, "good" means durable, pleasant-looking, and not unfashionable.

From what I've seen of the clothes that fat women are enthusiastic about, they tend to be somewhat simpler and more classic looking than the mainstream. I don't know whether this is making the best of what's available, or whether most thin women would prefer that sort of thing if they could get it.

Or maybe my perceptions of the difference are off. I'm actually not that interested in clothes.