heh.
yes, default is with makeup and natural is without, and both have an AO and no-AO version.

btw, if you are toggling the lip gloss on or off via MATs then make sure you use the same 'type' as the skin MAT you loaded. so if you are using the 'natural AO' skin then make sure you use the AO lip mats with it, otherwise you will get a small 'seam' in the shadows at the edge of the lip.

really there is no reason NOT to use the AO materials unless you have a slow computer or are doing preview renders and want to speed them up. make sure to check out the PDF tutorial when you get a chance as all this stuff is explained.

cheers,
-gabriel.