Actually the 24" IPS Dell has some serious issues with many monitors showing a green/pink tint when working with a white background. As the main reason to go IPS is desktop publishing that is a serious problem and Dell are being very difficult about it.
http://en.community.dell.com/support.../19648044.aspx
On the other hand the 27" Dell 2560 x 1440 IPS screen is by all accounts stunning.