On the whole "Dell 30" is ahead of Apple on Specs" issue, I really don't see much in it other than price and a media reader in Dell's favor. IE:
Dell's Specs from the Dell site:
Viewable Image Size 30 inches
Diagonal Size 30 inches
Display Type Active Matrix - TFT LCD
Depth 7.87 inches
Height
18.49 inches compressed
22 inches extended
Height Adjustability 90mm up or down
Swivel 60° left and right
Tilt 3° forward and 19° backward
Width 27.26 inches
Weight (no stand) 25.07 lbs.
Weight (with stand) 35.24 lbs.
Horizontal Viewing Angle ± 178° (typical)
Vertical Viewing Angle ± 178° (typical)
Color Support 16.7 million colors
Contrast Ratio 700:1
Response Time
11 ms (grey-to-grey)
14 ms (black-to-black)
Brightness 400 cd/m2
Resolution 2560x1600 (max)
Pixel Pitch (Dot Pitch) 0.250 mm
Ports
DVI-D (dual link) with HDCP
USB 2.0 (4)
9-in-2 Media Card Reader
Kensington security port
Power Consumption
147W to 177W (max) w/USB and sound bar
Less than 1W switched off
$2199 US before shipping
Apple's Specs from the Apple Site:
Resolutions
* 2560 x 1600 pixels (optimum resolution)
* 2048 x 1280
* 1920 x 1200
* 1280 x 800
* 1024 x 640
Display colors (maximum) 16.7 million
Viewing angle (typical) 178° horizontal; 178° vertical
Brightness (typical) 400 cd/m2
Contrast ratio (typical) 700:1
Response time (typical) 14 ms
Pixel pitch 0.250 mm
Screen treatment Antiglare hardcoat
User controls (hardware and software) Display power, system sleep, system wake, brightness, and display tilt
Cables DVI (Digital Visual Interface), FireWire 400, USB 2.0 and DC power (24.5 V)
Connectors
Two-port, self-powered USB 2.0 hub,
Two FireWire 400 ports and Kensington security port
$2499 before shipping
Of course price is an important issue. Personally I am not interested in a 9-in-2 media reader in th monitor as I only use CF, thus that's a wash. The Dell has 4 USB 2.0 ports, the Apple has 2 USB 2.0 and 2 firewire 400, also a wash as far as I'm concerned.
Other than these points, I see no technical differentiation between the two monitors in terms of specification or performance.