The contrast ratio differences are apples to apples in that matter. Firstly the difference isn't huge, and the much, much brighter DS Lite screens give a better real-world perception of contrast between colours anyway. The DS Lite screens also display 74% of the sRGB colour gamut for consumer content, which is super impressive for 2006. That's already what makes the DS Lite look more saturated than the washed-out PSP-1000 (56% of sRGB) and original DS displays.
Higher resolution is debateable given 1) the DS Lite had two screens of 256 x 192 anyway 2) the screens were smaller, so pixel count wasn't a huge deal, 3) the DS Lite's dual screen setup was better for the 2D-pixel art-type games DS became known for anyway.
You're also forgetting the PSP-1000's absolutely horrendous refresh rate - DS Lite didn't suffer from horrible trailing/ghosting artifacts when games were in motion. And very few PSP games actually ran at full colour depth - games which exhibited obvious dithering were displaying less maximum colours than a DS Lite could anyway.
DisplayMate's conclusions weren't based off those factors, but realworld performance of the DS Lite's display is more impressive than the PSP-1000's, whose only real perceivable benefit at the time was size and resolution.