PET (Polyethylene Terephthalate) is a plastic resin and most common type of polyester.
BOPP (Biaxially Oriented PolyPropylene Films) are produced by stretching polypropylene film in both machine direction and transverse direction.
Both label types will offer similar appearances and are high quality products. The main reason for the difference is the different needs of sheet labels and roll labels.
Check out our blog article on when you should use a BOPP label here.