AnandTech's comparison of these two monitors
This DELL monitor was reviewed by AnandTech. Among other things, they had this to say: "For one, Apple uses LED backlighting whereas the U2711 sticks with CCFL technology. But isn't CCFL worse? That depends on what you're after; the iMac 27 offers a 72% color gamut while the U2711 has a 102% color gamut (based on the CIE 1931 standard). Using RGB LEDs, it would be possible to get a similarly high color gamut, but our experience with RGB LEDs to date is that they cost more and consume more power than regular LEDs, so we can understand Dell's interest in sticking with the "older" technology. (We've only seen RGB LEDs in a few laptops so far, and as one example it's a $175 upgrade on the Dell Studio XPS 16 compared to a regular white LED display.)"
This DELL monitor was reviewed by AnandTech. Among other things, they had this to say: "For one, Apple uses LED backlighting whereas the U2711 sticks with CCFL technology. But isn't CCFL worse? That depends on what you're after; the iMac 27 offers a 72% color gamut while the U2711 has a 102% color gamut (based on the CIE 1931 standard). Using RGB LEDs, it would be possible to get a similarly high color gamut, but our experience with RGB LEDs to date is that they cost more and consume more power than regular LEDs, so we can understand Dell's interest in sticking with the "older" technology. (We've only seen RGB LEDs in a few laptops so far, and as one example it's a $175 upgrade on the Dell Studio XPS 16 compared to a regular white LED display.)"