NEC model is still very new so I don't think any reviews are out just yet,Dell have very good customer service so I would edge with the Dell,I know its 1920x1200 rather then the NEC 1920x1080 but if you did get any issues then Dell normally will replace the LCD without problem.
Personally I would go with the Dell,however I have not heard anything bad about the NEC.
Btw I forgot to say the Dell has better response time so should be better for gaming as well.