I wish I completely understood how paper and cardstock are rated and explained. It seems to be a complex topic...with the number weight designation depending on the type of paper (index, card stock, cover stock, etc).
I took a sheet (8.5x11)of Stampin' UP! whisper white, the Sam's Club Georgia Pacific and Papertrey Ink White and weighed each one on my electronic kitchen scale. (yes, I know, that weight has nothing to do with the "110 lb." designation, but it was the best way I could come up with to compare them.)
Sam's club = 12 gm
SU = 13 gm
PTI = 17 gm