https://www.rtings.com/monitor/reviews/ ... lite-xg270TheMadMan697
XG270 240Hz Overdrive Faster (Recommended by Rtings)

Is a technical limit, no way to avoid it completely.
Unfortunately, any IPS or TN 240Hz can fit 100% GtG response times into 240Hz. They would need under 4,16ms in all shades to avoid smearing. This limit cause contrast and color deviations in moving images, 240Hz non-strobed and 240Hz strobed (smearing without motion blur, but with crosstalk).
Until IPS tech evolve, no way. Or manufacturers change to MicroLED, that prototipes show nanosecond response time

Rise/Fall show 80% GtG transition. Until IPS evolve to offer real 4ms GtG in all shades, 100% transition and overshot free, if we want good image quality free of most part of this smearing, no motion blur, and almost crosstalk free, strobe well tweaked is here to help, but the requisite is 100-120FPS/Hz VSync.
With (100Hz 10ms) and (120Hz 8.33ms), much more 100% GtG transitions fit inside, and strobe reduce to much motion blur, result in very good moving image quality, smearing reduced, with almost the same color and contrast that static image, but add a bit of input lag, overall a good trade off except for competitive where each ms matters.
The only advantage of the ASUS is +40Hz (+16.6%), but is not versatile, can't show 100-120 FPS/Hz with like CRT motion in modern games that GPU can't move at minimun 280FPS.
Not all gamers play online competitive, there are games for instance locked at 60FPS like emulators (MAME DoxBox) that using software BFI with XG270 at 120Hz PureXP+, result in like CRT 60Hz feel. VG279QM can't do this.
If monitor is for competitive, VG279QM is a good IPS election, if is not exclusively competitive point of view, can be considered a more versatile monitor. But in Professional FPS leagues, players use TN, so, if decision is pure competitive, maybe the election is Zowie TN.
Also to take in account, is that VG279QM is not native 280Hz, is just 240Hz native panel overclocked. And Asus say that if your unit show artifacts at 280, down to 270, or less, the only officialy assured is 240

From this point of view, all 240Hz monitor are 280 "ready". We can use XG270 + CRU and create a custom resolution with 280Hz overclocked. The same on Zowie XL2746S. This +40Hz Asus advantage not seems to much solid ! Take in accound also, that overclocked LCD is force the panel. It remains to be seen if those overclock will last over time, or end with RMA.