There's also a notebookcheck review for the MBA and you could compare the display sections.
I glanced over it and it seems like there's no obvious way to compare the color space coverage and/or calibration.
The Dell screen seems brighter but I have always taken these brightness measurements with a grain of salt. I usually turn down the brightness on all my screens, since the maximum brightness usually hurts my eyes. I assume maximum screen brightness is important if you do a lot of work outside but otherwise I don't see the point.
