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Even 200 dpi would be fine with true 254 shades with black and white. But eink only just manages 14 shades in addition to black and white so antialiasing is limited. A 133 dpi laptop may look better in resolution than 227 dpi eink because it has close to 256 brightness levels, colour (close to 16M variations of hue, saturation and brightness) AND it has sub pixel addressing. A colour LCD or OLED at 133 dpi is effectively 266 x 266 or 399 x 133 dpi before anti-aliasing, which with 254 brightness levels of grey (and more if coloured) gives a visual appearance similar to about 1200 x 500 dpi laser or 1000 x 1000 laser, depending on the type of subpixel layout.
The less shades the more resolution is needed. That's why laser printers need about 1200 x 1200 to decently render 150 dpi 16.7 Million colour photos, each dot is either on or off, no levels at all. Ink jets for a while have been able to vary density to an extent by modulating the droplet size, so 600 x 600 dpi ink jet can do as well as 2400 x 2400 high end laser prints.
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