As much as I love Apple products, the ACD unfortunately is one Apple product I'd advise staying away from. They are long overdue for an update, and even so are gravely overpriced for that little they are. I personally can't justify paying the premium for something that just looks pretty. You can get much better monitors for less from the likes of Dell or Samsung. As for the iMac Screen, colours look nice since they're both glossy but I'm told that the 24" panel is better than the 20" so you're probably better off comparing them in store.