When the 900IFT says its .20mm dp, it's measured in a different way and can't be compared to the dp rating on most monitors. I own the 900IFT, it's a good monitor. But in terms of overall bandwidth and picture quality, the 900NF is better. The 900NF is an aperture grille/diamondtron like Geekish mentioned. Usually aperture grille monitors are inherently better when it comes to showing vibrant colors, or so I hear. The 900IFT is however a very high quality shadow mask.
I always heard text and such would look better on the 900IFT, but pictures and games would look better on the 900NF. Never seen the 900NF so I can't say for certain if this is true.