The Empire Worldwide ones are not accurate, but neither are the Fenix Props / Custom Props ones, although the latter are a bit better in some ways.
The Empire Worldwide ones are made out of a kind of satin. From a distance, it's hard to tell if it's leather or not. The strips are too wide for the screen look but they wrinkle nicely and could be good if you're replicating the Rebel Assault look of Vader (which used wider strips). The material appears to breathe quite nicely but may still be warm if worn outdoors under the sun and in conjunction with a wool robe, depending on how thick the wool is. I imagine a leather suit's heat buildup is worse unless its back is an open mesh.
The Fenix Props / Custom Props strips look too rolly polly and puffy, but if you're not super picky, you could convince yourself it's accurate, as many 501st costumers flock to it, and they're not quite screen accurate themselves.