Gaming PerformanceThe overall gaming experience of the Acer Predator XB271HU is sublime. This is mainly due to the fact that it is a high refresh rate panel supported by NVIDIA's G-Sync technology, which essentially adapts the screen's refresh rate to the current framerate to ensure a perfectly smooth, tear-free picture. The effective G-Sync range is 35-165 Hz (or 35-165 FPS, if you want to look at it that way), which means you'll be able to fully utilize it even if you decide to overclock the panel.
The smoothness of the gameplay and my mouse's accuracy when gaming at a high framerate are simply staggering. By getting this monitor, especially if you were previously using a standard 60 Hz model, you will effectively improve your in-game skills. Within a matter of hours, I started hitting headshots I previously wouldn't even dare to try. I also felt like I replaced my mouse with an infinitely better one even though that is not really possible as my mouse is equipped with one of the best optical sensors currently available, the PixArt PMW3366.
Overclocking of the panel can be done in a matter of seconds by changing a single setting in the OSD, and I had no trouble hitting the maximum 165 Hz mark. I'm pointing this out mainly because Acer's first overclockable monitor, the Predator X34, was a bit of a hit-and-miss affair. You could get a sample that was overclockable to 100 Hz, and your friend could get one that wouldn't go past 95 Hz, even though you bought them on the same day, in the same store. Not so with the Predator XB271HU. It goes up to what you set it to without a hitch.
Response Time and OverdriveAcer rates the Predator XB271HU as having a 4 ms GtG response time. The panel uses overdrive technology to make the pixel transitions faster, and you will find the option under the acronym "OD" in the OSD. Overdrive has three different settings - Off, Normal, and Extreme. I extensively tested all of them in various fast-paced games and used Pixel Persistence Analyzer to confirm my findings.
For gaming, I found the Normal setting to work the best. When Ovedrive is set to Off, there's noticeable ghosting in darker games. It's not worth setting it to Extreme, though, as that will introduce quite a lot of overshoot - that distracting, ugly-looking white trail behind moving objects. Setting it to Normal offers the best balance between these two extremes and generally results in satisfyingly sharp, nice-looking action.
Input LagI tested input lag by connecting the Predator XB271HU and my trusty CRT monitor to the same graphics card, putting them in clone mode, and running a precise timer, with V-Sync turned off. I then took photos of both screens at very high shutter speeds to capture the difference in the times displayed on the timer. While this certainly isn't the ideal method of determining the exact input lag value, it does give us an idea of the category the monitor falls into.
The general consensus is that, in terms of input lag, there are three categories monitors can fall into. If it's lower than 16 ms (that equals a frame of lag at 60 Hz), the monitor can be declared as gaming-grade for even the most demanding gamers. If it falls between 16-32 ms (between 1-2 frames of lag at 60 Hz), the monitor is suitable for almost everyone but the most hardcore gamers, especially if they're playing first-person shooters. Finally, if a monitor's input lag is higher than 32 ms (over 2 frames of lag at 60 Hz), even casual gamers should be able to notice it. Will they be bothered by it? Not necessarily, but I can't recommend a screen like that for serious gaming.
The Acer Predator XB271HU confidently falls into the first category. Its measured input lag was sitting well below 10 ms with Overdrive set to Normal. It did increase a bit when Overdrive was set to Extreme, but that's to be expected since the electronics have a more complex task to complete. That's eSports-grade performance right there and yet another confirmation of the fact that the Predator XB271HU is a great choice for the audience it primarily aims for.
ULMBIf you're after a complete elimination of ghosting, you'll be interested to find out that the Predator XB271HU supports ULMB (Ultra Low Motion Blur), a technology enabled by NVIDIA's G-Sync module, but one that cannot be combined with it, as it works at a fixed refresh rate. In other words, it's either G-Sync or ULMB. It annihilates the blur by having the backlight act as a strobe. However, if not implemented properly, it can introduce flickering. It also has a few other caveats.
If you want to use ULMB, you'll have to first disable G-Sync and lower the refresh rate to 120 Hz. Only then can it be turned on in the OSD. After you do, you'll notice that the brightness of the screen takes a big hit, and that's not something you can change or fix. A brightness of 80% with ULMB turned on is the equivalent of around 15% brightness with G-Sync enabled. Even though the Predator XB271HU exhibits no significant strobe crosstalk in ULMB mode, I think you're simply sacrificing too much - the brightness (and overall picture quality), adaptive refresh rate, and ability to go up to 165 Hz. And for what - to solve a problem that practically didn't exist in the first place.