You can get the D531 with a 1280 x 800 14.1-inch screen, or a 15.4-inch 1280 x 800 or 1440 x 900 screen, while the 14.1-inch D631 sports those latter two.
The 114 x 168 black-and-white screen sports nearly 20, 000 pixels, letting you view emails and a time readout in several fonts, along with watch faces and other indicators.