http://www.10paperairplanes.com/how-to-make-paper-airplanes/07-the-ring.html I am not an expert at this- just a high school student, so please explain this in fairly simple terms. Thank-you very much in advance!
The larger glider flies with a larger Reynolds number, so friction drag will be lower relative to lift.
Using paper of the same grammage (weight per area) would result in the same wing loading and the same flight speed, and the Reynolds number will grow linearly with glider size. If you look up in the linked answer how friction drag changes with Reynolds number, you will see that friction drag drops with increasing Reynolds numbers.