While it may seem that a two-ply bed sheet would be a better choice with the greater number of fibers it contains, this isn’t usually the case. Two-ply sheets are often rougher and less durable, as cheaper materials are typically used. Focus more of your efforts on finding the right material and weave, but do try to stick with one-ply sheets. 

Percale refers to the type of cotton weave used to construct the sheet and consists of a traditional criss-cross pattern of one thread over and one thread under.