UltraSharp is Dell's best, and its a IPS panel. The Utrasharp uses an AG coating so the screen is ant-reflective, where as the S2240T has a glass screen. The glass offers better richer colors and slighting better clarity but is highly reflective, so placement is very important. If your gaming FPS than the 8ms on the UltraSharp would be better.
I would personally take the UltraSharp unless you absolutely need a touch screen