There is someone on this forum who has both (name starts with J I think). Pretty sure he decided he liked the CRT for multimedia but the LCD for text.
The FW900 will exceed the 20WMGX2 in terms of contrast. No surprise there, it may be forever until LCDs really match the contrast of a CRT. The CRT has too good of a black level for the LCD to compete there. And yes, black on the 20WMGX2 is a dark gray with the lights off. Fortunately, it's a very consistent and faint dark gray so it is rather unbothersome. That's not to say a pitch black wouldn't look better.
Thing is, with a CRT there are no discrete levels of brightness. It's just a direct (though nonlinear) function of the voltage given to the electron gun (IIRC) at one particular area. The more voltage, the brighter the pixel. Due to the triad-like pixel arrangement, the CRT's image looks softer. Although the FW900 actually has a lined (AG) arrangement AFAIK so I'm not sure how the pic compares in terms of smoothness. I'm guessing the CRT still has the edge here as the IPS 20WMGX2's pixel lining is very dark.
For text, CAD, and static viewing, the 20WMGX2 will win any day. It will take a well-calibrated 20WMGX2 to match the FW900 with regards to color accuracy, and it will exceed it in that one area if properly calibrated. It will always fall behind in contrast, though you can mitigate this problem by using a higher contrast value which usually results in higher white, and LCDs tend to have highest contrast at bright white/semidark black. The OptiClear coating will enhance the black, but only if you have ambient light around. You don't need the light shining right at the coating, in fact you shouldn't do that since it will reflect like crazy off the coating, but just aim a light up at the ceiling and have it diffuse. That's the best config for the NEC.
My guess: you will prefer the FW900 for dark images, by a large margin. For grayish/midtone/soft images the CRT may win also. For bright and stark ones you may be amazed at the clarity of the 20WMGX2. For example, WoW may look better on the LCD while Quake or Wolfenstein are more CRT games. For Oblivion, I'll have to give the edge to the CRT as it usually reproduces dark lush, green grass better and smoother. And of course you can't forget update rate (response time). CRT wins easy here any day. For neutral grays, the CRT will win again. Despite the 20WMGX2 being best in its class (in the consumer/acceptable price sector), LCDs simply can not track the color gray accurately without shifts.
Of course, with the CRT you may potentially have poor geometry in comparison, and you will also have 2-3 subtle AG alignment damper lines running across the screen.
By the way, this is from my point of view as an image enthusiast. Your opinion of image characteristics may differ from mine.
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