There are plenty of things you should consider when buying a new monitor. I will consider just a few, but the most important aspects from my point of view.
1. Pixel density
Depending on the screen size and the distance you’re sitting away from it you need a different pixel density. A 5 inch smartphone screen needs for example a higher pixel density then a 65 inch TV screen.
Example:
1) 1280×1024 on a 19 inch screen: √(1280^2+1024^2)/19 ≈ 86.3 ppi
2) 2560×1440 on a 32 inch screen: √(2560^2+1440^2)/32 ≈ 91.7 ppi
Screen 2 will look sharper then screen 1, cause next to the higher ppi you will also sit further away.
2. Refresh rate
The default screen these days has refresh rate of 60 Hz. If you want your games look more smooth you should take a screen with a higher refresh rate, but take care that the FPS rate generated by the GPU matches the number of Hz. For 3D content (alternate frame sequencing) you should at least take a 100 Hz screen, then every eye gets 50 Hz.
3. Panel type
There are 3 major panel types:
| Category | TN | IPS | (M)VA |
|---|---|---|---|
| Response Time | good | average | bad |
| Color accuracy | bad | good | average |
| Contrast ratio | bad | average | good |
| Viewing angle | bad | good | average |
4. Housing quality
Often you just check out the directly comparable values, but also the housing quality is important. I tend to choose a monitor with a solid frame, cause the “frameless” ones I have seen had all a bad housing quality.