If you are looking for an Apple Product go with the iPad Air 2. If you dont care what OS and want a "retina" display go with a samsung galaxy tab s 10.5.
"Retina Display is a marketing term developed by Apple to refer to devices and monitors that have a resolution and pixel density so high – roughly 300 or more pixels per inch – that a person is unable to discern the individual pixels at a normal viewing distance. Apple's Retina Display made its debut on 2011's iPhone 4S, which featured a 960x640 pixel screen with four times the number of pixels (326 pixels per inch) as the iPhone 4."