Open box is a return usually for a reason.
A return can be made for a simple reason like wrong product sent.
Or, it can be for some sort of a defect like too many bad pixels.
For such an expensive purchase, I think I would buy new.
But, if newegg has a suitable return policy for the monitor(particularly open box) in case of defects, I would consider it.
One thing to nail down is what is considered as bad pixels.
A nominal number is considered ok unless they are in the center of the viewing area.
If you buy the open box, it should be simple enough to test for proper functioning and bad pixels.