the old one is not really "better", in fact its actually more complicated to use and less compatible since, to my knowledge, it only accepts a YUV signal.
We're about to set up a z24x here and have it run via ultra studio mini-monitor, I have seen mostly good reviews from it the only "problem" is the uneven backlight bleeding but it seems to actually be the coatings on the panel reflecting on each other. Either way, for a 500 dollar color grading screen you really can't go wrong
I bought one and I have found the coating issue to be really bad. Where did you read about this?
It's much better when displaying bright footage, however.
I don't think the z24x is meant to be a direct replacement for the 2480zx. HP have had a rethink of their price points, and given the pricing and specs, I think they're expecting those who would've bought the 2480zx to go for the z27x.
It's still outdated relative to the z24x because of its last-gen HDMI and Displayports (1.3 and 1.1, respectively)