300 dpi/ppi is the recommended resolution at your final image size. The more dots/pixels the image contains, the sharper the image will print. As a result, printing may look blurry or pixelated if a 72dpi image is used as compared to using a 300dpi image.
Example above: First image (left) 300dpi/ppi vs the second image (right) at 72dpi/ppi