After all the tests are complete it's evident that performance differences between the MG278Q and MG279Q are fairly small. Color, grayscale and gamma accuracy are similar enough that it will be hard to tell the two apart in a side-by-side comparison. The all-important input lag and response tests are so close that even the quickest gaming hands won't be able to discern between them. In fact, the only tests where the more-expensive screen won decidedly were contrast and viewing angles.
Obviously off-axis image quality is a strength of IPS and a weakness of TN. We maintain that 28 inches is the absolute maximum practical size for a TN panel. Anything larger will suffer from poor detail and color shifts at the sides even when viewed from the front. IPS on the other hand can be much bigger with no visible degradation in image quality. And it works better in two- and three-display installations.
In the case of the MG278Q, we saw the expected result in our photos of test patterns but during actual use, gaming and otherwise, there was nothing to tip us off to the fact that we were looking at a TN monitor. Shadow detail stayed consistent in all areas of the screen even when the image was very dark. It was easy to see every nook and cranny of the freighter in the opening scenes of Crysis 3, for example.
The only area where the more expensive MG279Q has a clear advantage is contrast. Not only did our calibrated test results differ by over 28 percent, we could see the extra depth in the IPS panel's black levels. Both monitors have similar brightness so it comes down to the quality of darker material. No LCD monitor renders a true black; it's always some shade of gray. But if you nit-pick about contrast the way we do, the MG278Q gives away a little quality for its lower price.
Last is the difference in FreeSync range. Both monitors will run at 144Hz but only the MG278Q can stay in FreeSync mode up to that number; the MG279Q tops out at 90Hz. To run faster you'll need to use V-Sync or simply lock the max framerate to 90 in your game. Is that a big deal? That depends on the speed of your video card.
In our system, the R9 285 we use can't run above 100fps at QHD resolution in any title, so for us the limitation doesn't matter. But if you've invested a lot of cash in a high-end AMD graphics board, the MG278Q may be a better fit. If you can push QHD resolution up to 144fps, the choice is clear.
So if you need FreeSync operation up to 144Hz, and you'd like to save a few bucks in the process, and you don't mind using a high-quality TN panel, then the MG278Q is a great choice. We enjoyed gaming with it and think you will too.