The poly-cotton is blend of polyester and cotton. There are few percentages in the market such as 50% cotton/50% polyester, 20%/80%, or 30%/70% and so on. The cotton fabric is more breathable, nature and costly. But if printed, the color is more easier to be faded away. The printing is less vivid than printing on poly-cotton.
Poly-cotton can be more vivid printing, less shrikage after washing, feels smoother, and less expensive.
So if used for bed sheet, cotton is better than poly cotton. If used for drapes, table linen, or backing of blanket, the poly cotton even polyester fabric should be better.