that was exactly the choice I had to make last month.
I settled on the Dell in the end.
The NEC is a great looking monitor. It is basically a CRT monitor with an LCD footprint. the Opticlear finish gives it a distinct edge in terms of crispness and clarity. But it does create a LOT of glare. I was expected some glare and thought i was prepared for it, but there was WAY more than i expected. Even in my office with no light sources behind the screen. Basically, day or night, ANY light in the room will reflect off of you and onto the screen, especially when displaying a dark image.
the glare is by no means a deal breaker on this screen, but it did surprise me.
As for other performance, I managed to get both monitors side by side showing cloned desktops (ie both screen showing the same thing). And the Dell is definitely brighter (again, I describe the NEC as looking like a CRT because it is both sharper and dimmer than most LCDs). Color reproduction was decent with both, altough the NEC made things MUCH easier to adjust, with different presets for color temp etc AND manual adjustments. The Dells has a few very poor preset options, but does allow a small amount of manual tweaking. But i found the Dell much hard to adjust to my liking.
Component video performance was definitely better on the NEC. the default settings on the Dell are just horrible: wildly oversaturated. But with some RGB and saturation adjustments, I was able to get an image that I happy with on the dell.
Scaling options were definitely better on the Dell. NEC offers no scaling whatsoever, and seemed to make things difficult for my videocard, since even the video driver scaling settings didn't always work on the NEC.
NEC's TV performance was pretty good. definitely adequate for a secondary set, but too small for primary use as a tv.
Dell had much better stand, with height, pivot, pitch and tilt adjustments. NEC can be adjusted only in pitch.
In the end, I took the Dell because I liked the extra real-estate and was able to tweak the colour settings (both for DVI and component) to where i was happy with them. the cost difference was less than $80 after tax and I preferred the adjustability of the Dell AND the lack of glare. But it was a VERY close decision.