For me, this is my checklist:
165 Hz, 2560 x 1440
Response Time < 5 .0 ms (real, not what manufacturer advertises)
Combined Lag < 5.0 ms (real, not what manufacturer advertises)
ULMB or equivalent Motion Blur Reduction technology (120 fps)
AuOtpronics 10 bit IPS panel
Acer XB271HU and Asus P279Q meet these specs but Asus has recently switched to an 8 bit panel. There's Freesync version for Asus is MG279Q that you can look at but they don't have any MBR technology.... The G-Sync models from Asus and Acer listed are 165 hz, I have not seen Freesync models that are 165hz. But these are outta range at $525 and up.
The Asus Freesync 144 hz model is $450 so a bit outta ya budget range. Acer has a very good TN version which can be had for $325
Acer has an IPS screen for under $350
Acer Nitro Gaming VG271U Pbmiipx 27" Black IPS LED HDR400 FreeSync Monitor
2560x1440 Widescreen 16:9 1ms VRB Response Time 144Hz Refresh rate 400 cd/m2 1000:1
right now it's $299 w/ + $20 off w/ promo code EMCTDTC25, limited offer
Buy Acer Nitro Gaming VG271U Pbmiipx 27" WQHD 2560 x 1440 2K Resolution 144Hz 1ms HDMI DisplayPort AMD FreeSync HDR 400 Built-in Speakers Backlit LED IPS Gaming Monitor with fast shipping and top-rated customer service. Once you know, you Newegg!
www.newegg.com
It has an 8+2 bit Innolux IPS-type (M270KCJ-K7B) panel.... its the same panel used in the Gigabyte Aurus reviewed at the link below. As expected, it has some issues not seen in the AUOptronic pabels but they cost a lot more. And again as expected, the Freesync still has some issues at certain settings and blur reduction mode has some way to go to match G-Sync's ULMB. But of course, that G-Sync ULMB hardware module costs money. Acer has been at this quite a bit longer and I expect they will do a bit better at the overshoot and perhps someother issues as well. yes, there's things to pick on, but it has be be taken in context that this is a $300 monitor and can't be expect to compete with the $550 ones.
"The Aorus AD27QD is an interesting option in the gaming market, and it's nice to see a new manufacturer emerge with something a bit different to offer. We were impressed by the massive range of features, options and extras provided with this screen which gives it a premium feel and something that enthusiasts are going to enjoy tweaking, updating and optimising over time. Gigabyte have done a good job with the performance too and we were pleasantly surprised by the capabilities of the new Innolux IPS-type panel they've opted to use, in place of the well-established AU Optronics panel used by most of the competition.
Gaming is the primary focus of this screen of course and we felt the screen performed well overall. Some areas were excellent, including the input lag, high refresh rate capability and massive range of extras and options. Along with the native FreeSync support, Gigabyte have even had the screen certified as G-sync Compatible by NVIDIA which should give some further assurances about its VRR capabilities. Response times were on the whole pretty good, and behaved similarly to many other FreeSync screens. They were particularly good at maximum refresh rate, although perhaps being pushed a little too hard at the cost of a bit of overshoot. They were a bit more variable for lower settings and in VRR situations. That's one area where we've seen better stability and performance from hardware G-sync module screens, with many FreeSync models struggling in the same way as this model. That's not to say that performance isn't good at lower refresh rates and with VRR, it's just not as fast as it maybe could be. One area which wasn't so good was the blur reduction mode, which had too much strobe cross talk, poor peak luminance, reduced contrast ratio and lack of much user control. Perhaps it can be improved for a future firmware release, but right now we didn't find it very useful.
The IPS-type panel provided typical all round solid performance with wide viewing angles and good colour rendering. The use of a wide gamut backlight separates this from most other gaming screens at the moment and will be welcome for gaming and multimedia by most people we're sure. There is an sRGB emulation mode options offered which is useable, but a bit inflexible in terms of user control sadly. Not perfect, but something. Default setup was good and there was a strong contrast ratio for an IPS panel. We won't talk too much more about the HDR capabilities, or lack of, but that is common on most screens of this kind of range anyway."
More here:
https://www.reddit.com/r/Monitors/comments/ayflnj
https://www.reddit.com/r/Monitors/comments/aijnxu
As for alternatives, whatever you look at, make sure that you check the real specs at tft central. If its worth having, it's been tested on TFTcentral. Also they do a good job of explaining oft confused terms like "Bleed" vs "IPS glow". The latter will be found on every IPS panel where the former is not generally found on quality units. It is much more noticeable on a wide curved screen as it is more visible the further you get from the center of screen.
Pulse Width Modulation (PWM) Pulse Width Modulation is something you will hear talked about quite a lot nowadays. We have a full detailed article about PWM which is worth reading....[click link for more]
www.tftcentral.co.uk
Bleed or Backlight Leakage -
https://www.tftcentral.co.uk/features.htm#backlight
IPS Glow -
https://www.tftcentral.co.uk/features.htm#ips-glow
