All of these properties have an effect on the actual folding of the paper, but, when it comes to flying paper planes the three most important are: stiffness, weight, and texture.
You can refer to the PDF file for more detail on why these properties are so different for different brands of paper.
I have not checked Kmart or Target yet to see if they have changed their paper types.
As a note, the paper they have sold before ("Hots" from Georgia-Pacific, and "Brights" from Riverside) were better than "Embassy Colored Paper".
This causes a decrease in lift and an increase in drag, thereby, shortening airplane flight time.
(See the Foil Sim, full version, software page and using flat plate wing add a little camber and watch the improvement.) Worse, one wing can bend while the other does not and the lift and drag become unbalanced leading to instability.Most paper gliders have wings that produce more then enough lift to compensate for the heavier weight as long as we maintain a good speed. This usually leaves us to compromise at a paper that is 24 lb weight.You can search out the details of why paper is labeled under the weight values you see on the package but I am going to just present a table at the bottom of this page that show the weight values and equivalent thicknesses.Unlike full size aircraft, we are trying to get as much weight as possible built into our paper airplane.The reason for this is to give us the most momentum to overcome drag.First, most poster board or heavy craft paper for scrap booking does not even give a weight (most poster board is about 140lb index stock).When weights are given you might see 65lb or 110lb card stock.It requires more processing time to reduce stiffness and produce a softer paper.This increases cost and in order to provide the most competitive price most stores are selling lower quality paper."Hots" is fairly good and "Brights" is OK but a lighter paper.Weight is the next important property for airplane flight.