oh, you know Mr. C.... ACD = Apple Cinema Display.
John, the 24inch is an S-IPS panel which is preferred for photos. and PVAs are better for video. <<those are generalizations. If you want a head splitter I will look up my research links. but they may be at work.
I have not compared the two myself. But as an Apple user (home/work) I had to make a difficult move and get my first non apple display (after CRT and 20" ACDv1) because the new ACDs just don't cut it for calibration/consistency. I went with a NEC 2490WUXI (an S-IPS panel) with the Spectraview Calibration tool. Calibration is essential if you end up printing your images, which is my goal. I am just getting to understand all this. The NEC looks PCish (cringe) but you gotta make that sacrifice sometimes. function over design. 80% of my friends who have monitors have ACDs.
cheers,
ed