After looking at all my choices, I ended up with a 3440x1440 100 Hz Ultrawide monitor with G-Sync and an IPS panel. The ASUS PG348Q. I went with 3440x1440 for several reasons.
My first reason is the ability of the human eye to see small details. I sit somewhere between 30" and 36" away from my monitor. With a 3440x1440 monitor at the 34" monitor size, the pixels are smaller than the resolution someone with 20/20 vision can easily distinguish when they are 30-36" away from the monitor. At 30" away the human eye can see the equivalent of 0.222mm dot pitch. At 36" away the human eye can can see the equivalent of 0.266mm dot pitch. A 3440x1440 monitor is right on the edge of visual acuity for most people at that distance. Now if you sit with your face 18" away from the monitor a smaller dot pitch may help, but if you have to sit that close, you may be blind and not able to distinguish the difference anyway.
My second reason is a 4K monitor with the same dot pitch would be very large. A 34" 3440x1440 monitor has the same dot pitch as a 40" 4K monitor. I thought a 40" monitor would be too big for my desk and for general use. I'd be turning my head side to side and looking up and down, unable to appreciate the full field of view. A smaller 4K monitor wouldn't give me any better image quality at 30-36" away from me because the pixels would be smaller than the human eye can distinguish.
My third reason is in game performance. Last summer, the newly released GTX 1080 still struggled to manage 60 FPS at 4K in many games without turning down the details and graphics quality settings. Playing games at 3440x1440 will yield better FPS than 4K with the same graphics card. Some games that can't manage 60 FPS at 4K can manage 80+ FPS at 3440x1440 witht he same GPU. A 3440x1440 monitor is 4,953,600 pixels while a 3840x2160(4k) monitor is 8,294,400 pixels. That's a difference of 3,3408,00 pixels(a difference of almost as many pixels as a 2560x1440 monitor) that the GPU has to output and that's why games that struggle to play at 60 FPS at 4K play great at 3440x1440.
When choosing a monitor, you need to take into consideration:
- How far away you will be from the monitor
- How much detail you want and do you mind seeing pixels.
- Do you want higher refresh rate and/or adaptive refresh rate?
- How much space do you have for the monitor.
- If you buy an adaptive refresh rate monitor, is it compatible with your GPU.
- Can your GPU handle the resolution? How long until your upgrade your GPU?
- Do you play games that require a higher or benefit refresh rate or can you use a standard refresh rate?
- Can you tell the difference between 60 Hz and 100+ Hz?
- What connectors does your monitor and your GPU have?
- What panel type do you prefer? IPS? TN? VA?
For those curious about dot pitch and pixels per inch, here is some dot pitch and PPI info:
3440x1440 34" = 109.68 PPI or 12030 PPI² or 0.2316mm dot pitch
2560x1440 27" = 108.79 PPI or 11834 PPI² or 0.2325mm dot pitch
2560x1440 32" = 91.79 PPI or 8425 PPI² or 0.2767mm dot pitch
3840x2160 27" = 163.18 PPI or 26627 PPI² or 0.1557mm dot pitch
3840x2160 32" = 137.68 PPI or 18956 PPI² or 0.1845mm dot pitch
3840x2160 40" = 110.15 PPI or 12132 PPI² or 0.2306mm dot pitch
3840x2160 43" = 102.46 PPI or 10498 PPI² or 0.2479mm dot pitch
Monitor resolutions and the number of pixels:
1920x1080 = 2,073,600 pixels
2560x1080 = 2,764,800 pixels
2560x1440 = 3,686,400 pixels
3440x1440 = 4,953,600 pixels
4096x2160 = 8,847,360 pixels