They are just the default folders - as long as both are listed in DS as Poser Content Directories (that is, they appear under Poser Formats in the Content Library pane) then you can generally use either. The only exception would be new morphs for the fourth generation figures, which may need to go in the directory you used for the base figure. Your content directories can be anywhere and called anything (and as long as you don't put one inside another, or put them in a protected location like Program Files or Windows).