Funny you should ask this question as I was just wondering the very same thing myself, I've spent the last 2 days researching it. Now I bought an HPZR24w when they first launched last year, I sold it a few months ago which I am now regretting, I thought switching to a 1080p display would be a good idea, not because I didn't want the extra vertical resolution but because my laptop is 1080p and so is my tv, thus it gave me great flexibility in using clone display on the tv ...which I don't actually do at all now and using the display on my laptop (because of some of the stuff I run it's handy to not have to make any changes) ...however a few months down the line I regret it deeply and wish I had never sold my ZR24w and I want a 1920x1200 24" IPS display again.
So here I am now considering buying the same damn thing I sold ...I call that a 140 pound lesson
Anyway I found the ZR24w to be largely excellent, although I did have one little niggle with it, I found the monitor suffered from a mildy distracting amount of IPS glow in the lower left corner of the display when using prpgrams with dark backgrounds, this was never really a problem on the desktop but it was a bit annoying in Eve Online, which I play quite a bit of.
Anyway that brings me to wondering about the Dell U2412m now, my research suggests that technically the HP should be superior in absolute terms, with it's full 8 bit panel and high grade CCFL backlighting ...however I have read more than once that people who have used both prefer the Dell.
I know that pretty well any IPS display over a certain size is going to suffer from IPS glow to one extent or another. However the smaller Dell 2209w's I had before the HP did not, at least not in anyway I could notice ...indeed they were actually the best monitors I have ever had in terms of display quality (I've had 13 lcds to date, so quite as few) ...I just found the resolution a bit restrictive after coming from a Dell 2407 before those ...hence the change to the HP. I guess the lack of glow from the head on position with these was largely due to the smaller size.
In essence I can't really tell you which is 'best' ...it's rather subjective, but based on specs the HP 'should' be ...however it's not really that simple and it doesn't necessarily seem to be a case of the 8 bit and CCFL > 6 bit + AFRC with LED panel like you would expect.
I'm not sure what to do myself, I am a bit reluctant to buy the same display again though.
One thing you should bear in mind is that the hardware scaler on the HP did not used to fuction ...I don't know weather HP ever did anything to fix that ...I assume they did, but that's a bit assumption. This wont affect you though unless you intend to run a games console into the display playing a 16:9 picture ...the HP wont scale it correctly it'll stretch it and distort it ...at least it will if the scaler issue hasn't been fixed.
Although I didn't really want to spend much more than 300 pounds I am considering just pushing the boat out and going for a Dell u2410 and ceasing my unhealthy and expensive monitor habit. If I just buy the best 24" (short of seriously expensive pro models) there is with all the specs I could want ...I'll probably just stick with it for a few years. One way or another though I can never quite find the perfect monitor and if I keep buying the more 'compromised' models I will probably keep chopping and changing and wasting money.
I know it's of rather less importance than the performance of the display ...I must say I don't actually like the new Dell Ultrasharp design aesthetics as much as I did the old ones, I prefer the more angular and I must say more 'expensive' and solid look of the older models. The HP has a nice design too, solid, businesslike and functional with a feeling of quality.
Incidentally I bought an Asus ML249H 24" MVA monitor not long ago, to see how MVA panels are these days and because I knew it wouldn't have IPS glow, well ...the contrast ratio was great but it's accuracy with colours was crap, had terrible banding, far worse than the TN display I am typing on right now and had right next to the Asus. The one I got, had a small crack in the bezel too, although it didn't seem to have affected the panel in anyway I obviously couldn't keep a unit with a crack ...but like I said I wasn't very impressed anyway, other than the contrast ratio and very light AG coating ...which gave it a semi-gloss effect, that was nice, really helped with colour 'pop' ...for the lighter colours especially. Also this particular display has dreadful build quality, nasty cheap plastic and a crappy stand ...although I knew that when I bought it to be fair, I just thought I'd give it a chance.
Edit: Well with the offer price today I decided to take a punk on the Dell U2412M, I'll probably post some thoughts on it when I get it.
