We have NEC PA301s and PA302s and Eizo CG319s. You will be able to effectively soft proof with either display. Both are excellent. The Eizo is better in several ways. First, switching between different calibration settings is fast - roughly 3 seconds from one to the next. Whereas with the NECs and Spectraview ll, it takes a couple of minutes to switch between each calibration set. If you have a viewing booth near the monitor the Eizo, through ColorEdge, allows one to use a colorimeter like the i1Display Pro 3 to read the brightness and white point of the paper stock on which you print which it then records and adjusts the screen accordingly. With the NEC it involves more trail and error to get that match. The colour correction sliders are similar to those found in Lightroom or PhotoShop. They allow one to tweak the colour response to get even closer to the image in print. General calibration is done without having to stop working. The Eizo blacks are cleaner than NEC insofar as there is no IPS glow whatsoever.
At the end of the day, I would say that you won't go wrong with either a high-end NEC or the Eizo. The Eizo is faster. I have equal confidence in both in terms of display accuracy. The Eizo is a gem if one can afford it. In terms of image display and soft proofing, the ability to switch quickly between calibrations makes it easier and therefore more acceptable to switch back & forth to ensure the correct setting is used.
I hope this is somewhat helpful.