I know someone who owns the Dell monitor, it's amazing, but I'd say go apple if it's cheaper. personally, I'll never need more than 20 inches for gaming.
The Apple 30" is way cheaper now. $1999 unless you're a real person who goes to the Education Store at www.apple.com, at which point the price is $1799.
if you use TV resolution for your computer, you'll barely be able to make out the start menu and other buttons and stuff... priorities would be
1) resolution (when considering large screens)
2) response time
3) size
notice how the price CATAPULTS going from 22 inch to 30 inch. there's a nice acer 22inch widescreen monitor for like 200-300$, and you go up 8 inches, and the price goes up by a factor of 8!!