Long answer to a short question:
The XL2546K looks a lot better to me with its balance of colors, gamma, brightness, etc. and is way more customizable than the XG2431. PureXP+ is every so slightly more clear than DyAc+ (both are very clear though), but you lose a lot of brightness with PureXP+ where you lose none with DyAc+. The highest two levels of PureXP+ (Extreme and Ultra) are practically unusable given their low brightness.
The XG2431 seems to give me eye fatigue/headaches where I'm not totally sure the XG2546K does. However, there's a chance I'm someone who gets fatigue/headaches from strobing and that neither monitor is going to be an excellent fit, as I've never had eye fatigue/headaches on any monitor I've used for the last 20 years (and I've been a PC power use the whole time). I'm actually using both monitors side-by-side right now still but with strobing off on both and it seems to be okay, so the issue could be strobing overall.
In general, I just much prefer looking at the XL2546K for all applications over the the XG2431.
However, and I don't know if this is specific to TN panels, BenQ, the XL2546K, or what, but I get some pretty bad text smearing/ghosting when scrolling through vertical text. I use my setup to work from home for 7-9 hours a day outside of gaming, and this text smearing/ghosting is probably going to be a deal breaker for me.

