There isn't any correct or incorrect, petticoats are completely unsentimental. They're supposed to give shape to the dress and smooth out any bumps from hoops or other understructure, and as long as they do that you're golden.
Depending what you're trying to do, the second option seems like it would work better for most purposes--it has a smoother surface line and less bulk around the legs.
Tom Petty [Final Fantasy XV] (9%)
Bondage Finch [Bondage Finch Adventures] (12%)