· The first choice to make is resolution. The sweet spot has been at 2560x1440 for the past several years. If you were one of the handful of people who got an RTX 3080 during the mostly paper launch, you can probably do okay at 3840x2160, but for the rest of us, 2560x1440 is a better choice for gaming performance.
· Refresh rate: High refresh gaming is a good thing. This is much more important if you play first person shooters, but even MMORPGs and strategy games look better at high refresh rates. Let's look for 100 Hz or higher refresh rate.
· Variable refresh rate: Once NVidia quit blocking VESA standard adaptive sync in their drivers (as long as your have a GeForce 10x0 or newer), that killed off expensive proprietary G-Sync in favor of the VESA standard adaptive sync that AMD has long supported as "Freesync" (and that NVidia now calls "G-Sync compatible"). To support low-framerate compensation (LFC), the lower limit of the Freesync range needs to be less than half of the maximum frequency. If your framerate drops below the minimum, LFC allows the graphics card to automatically double each frame, so you still have tear-free Freesync gaming. This is a great feature.
· High Dynamic Range (HDR): This will eventually be a nice thing to allow whiter whites and blacker blacks in games, but getting it to work properly on the Windows desktop and in your games can currently be a bit of a chore.
Any monitor labeled as "Freesync Premium" supports Freesync with 120Hz or higher maximum refresh rate and LFC. This is an easy checkbox to look for to get features that are very desirable.
"Freesync Premium Pro" adds HDR
AMD maintains a handy list of Freesync monitors here:
https://www.amd.com/en/products/freesync-monitors
·Size: For 2560x1440, you probably want a 27" to 32" display. For 3840x2160, you're more likely to want a 40-43" display. This would be less of an issue if Windows applications did a better job of scaling, but if you get one of the smaller 2160p monitors, some icons and text are going to be too small to read unless you're leaning in very close.
·Panel type: The three major LCD panel types are TN, IPS and VA. TN is the cheapest and the fastest, but it changes color and contrast if you view it from anything other than directly perpendicular to the screen. This defect of the technology makes TN unsuitable for large monitors and useless for photo editing or anything else that requires accurate color.
IPS panels are generally considered the best balance between speed and color accuracy. One drawback of IPS panels is that blacks may not be very black. In a totally-dark room, they may look gray. You can fix this by keeping a lamp on in the room when you're gaming.
VA panels can produce darker blacks than IPS, but they generally have the slowest pixel response. This can vary significantly from one monitor design to another.
When you've found a monitor that has all of the features that you want, read reviews at RTings and TFT Central to see how your particular monitor actually performs.
I'm quite pleased with the Dell S3220DGF, which I got for $360+tax at Best Buy.