iReader Smart X3 is the first E Ink tablet with a Carta 1300 display
iReader Smart X3 is the first E Ink tablet with a Carta 1300 display

liliputing.com
iReader Smart X3 is the first E Ink tablet with a Carta 1300 display - Liliputing

I personally care only about the contrast, so you can stop loosing details in shadows on manga
Contrast is huge if you read books at night in white text on black "night mode" too. That's how I do almost all of my reading now and I'm not particularly satisfied with the contrast on my Carta Plus reader.
Current tech is a bit like reading white on black newsprint, the contrast just isn't great.