Well this is a complicated question that is totally dependent on your own personal preferences so its hard to answer but I can tell you my experience. Back in 2011 I originally had a couple of 580 Lightnings which I was really interested in utilizing to their full potential so I decided to buy a Samsung S27A950D (which is just a fantastic 120Hz monitor). Let me tell you that the "awesomeness" of 120Hz that everybody claims is 100% accurate! Just the smoothness of moving the mouse pointer around on the desktop is sublime! In games there is no tearing and no lag from having to use VSYNC. For over a year I absolutely adored my 120Hz monitor. Then one day I went to CompUSA and saw a brand new Samsung monitor I'd never seen before: The S27B970D. This, of course, is their bite-the-back-of-your-hand gorgeous PLS monitor that has that glorious 2560 x 1440 resolution standard. I played around with that monitor for probably an hour in the store and by the time I left was truly bitten by the high resolution bug. I wasn't about to spend $1200 on the S27B970D (although I really wanted to) but at the time the Korean IPS craze was just starting up and I found the Achieva Shimian IPSB that, with its tempered glass front, was a suitable doppelganger for the Samsung. While I had absolutely loved my 120Hz monitor for over a year by this time I simply had to try out 1440p on my PC and so I sold the Samsung and found two of the IPSB's right here on OCN's marketplace (which I got together for about what I sold my Sammy for). I still have the Shimian's to this day.
Now for my experience with the two different monitor technologies. First, let me say that I really do miss the 120Hz fluidity of that Samsung, especially when gaming. I could literally sit there and drag windows around on the screen and be thoroughly entertained by how smoothly they moved! In games I have had to get used to tearing as a way of life since I can't abide by the lag of VSYNC but with the 120Hz monitor I could run around in Crysis or Battlefield, looking left and right and it was literally butter smooth. Now the trade off with 120Hz at the time of course was that I was stuck with 1080p, which now that I'm used to 1440p, is almost unbearable! My folding rig still has my old 1080p monitor (60Hz) and whenever I use it I can't believe how fuzzy and magnified everything looks. I know that sounds like an exaggeration but after having used 1440p for so long it really looks that bad. And therein lies the conundrum. As much as I miss that fluid and smooth experience with the 120Hz monitor, I could never go back to 1080p on a computer monitor ever again. Period. And so here I am, a year later and missing 120Hz terribly but unable to go back because the picture quality of 1080p is just not good enough for me anymore. Gaming at 1440p is fantastic but its everything else I do on my PC that also makes 1440p indispensable. Now I am starting to get excited by these new monitors coming out that promise 120Hz AND 1440p resolution (though they are not IPS) and I may start to think of finally replacing my Shimians, but not yet.
The next conundrum I can already see: Do I go with a gorgeous 50" 4K TV as a monitor at 60Hz or do I get one of these new 1440p 120Hz monitors???? Gaaaah, I hate making choices!
