I think you're going to get a lot of different answers.
Here's how I ended up with the LG 34UC79G, your priorities may be different:
I'd had a Samsung P2450h (24", 1080p, 60Hz) for several years and while there wasn't anything wrong with it, I wanted to try something different. I currently have a GTX 970 and, depending how the custom designs work out, I may get a Vega 56 in a few months. The last real top end Nvidia card I could afford was the GTX 580, so whatever monitor I went for wouldn't be powered by a 1080ti or a Vega 64. So whatever I went for, it had to be usable with a GTX 970 in the short term and a Vega 56/1070 class card in the longer term.
Incidentally, this is also why I didn't consider a G-Sync monitor.
A lot of what I'd read suggested than 27" 1440p was the natural successor to 24" 1080p. A friend of mine has a 27" Benq 1440p, 144Hz Freesync monitor running on a Ryzen build with a R9 290X and he let me spend an afternoon gaming on it. The monitor was very nice, extremely clear, but at 100% scaling I found the text a little small. I felt that I might need to use font scaling in Windows, which would reduce the benefit of the extra desktop space from the higher resolution. Your eyesight may be better than mine!
On to gaming. I had a go at Doom, and although the monitor was much nicer than what I was used to, once the action started the experience was actually very much the same as my 1080p Samsung. Don't get me wrong, it looked nicer, but the experience felt the same. Also, I had a framerate counter running and performance was quite a bit lower than I was used to. The 290X would be faster than my 970 at the same resolution, but on the 1440p monitor the 290X was having to push around about 78% more pixels. I also had a go at Planetary Annihilation: Titans and again, the higher resolution was nice, but it didn't make a massive difference to my enjoyment of the game.
I would have liked to have seen an ultrawide monitor in action before I bought one, but unfortunately that wasn't an option. That was one of two reasons why I didn't go for a 3440x1440 screen: They're very expensive to buy before you try, and secondly they have about 138% more pixels for my GTX 970 to push around. After the performance hit I observed on the 290X at 1440p, I realised I couldn't afford a powerful enough PC to get the performance I would want.
That left 2560x1080. The common wisdom is that really you want a 29" screen for this resolution, but with the current deal on the 34" LG I took a chance and I'm glad I did. I honestly couldn't be happier with it. 21:9, even at 1080p, is much better than 16:9 if you usually have two windows open side by side on the desktop. I was worried that text would be too pixelated but at the distance I sit from it I haven't found this. Again, I wear glasses so your eyesight may be better than mine and you may find this an issue.
I find gaming at 21:9 much better than at 16:9. I've got to admit when people have talked about it being a more immersive experience I hadn't really believed it, but it does make a big difference. The first thing I ran was Doom to get a fair comparison and the extra width really does change the experience. Plus the performance hit isn't anywhere near as bad as I'm only asking the GTX 970 to push 33% more pixels than before.
While I like a good FPS I'm more of a casual player and more of my time goes on RTS and MMO games. I've been back on the old Lord of the Rings Online lately and 21:9 gives a much better impression of being in a huge open world than 16:9 ever could.
Anyway, that's my experience, with a few caveats:
- If you've got great eyesight, try and find a 34" 1080p monitor to look at before you buy.
- If you can afford the graphics hardware to push it, not to mention the monitor itself, I'm sure 3440x1440 is worth it.
Im hoping for the system to last the next sort of 5-7 years without upgrading
