In the true meaning there is no polyester based paper, as there is no paper in the true sense involved... (Don't know in which drawer to put it.)

The base is formed by a polyester sheet. Which means:

-) greater mechanical/dimensional/chemical stability

-) a smoother surface (higher gloss) can be produced than on sheer and PE coated paper

-) greater longivity than PE coated paper
(It should also have a greater longivity than a sheer paper base, but there still is the emulsion as limiting factor in those two cases.)