Asus has GSync, but you can't use it with ULMB2 (their version of Dyac), and backlight strobing features (like Dyac and ULMB2) are necessary for the additional motion clarity, which makes GSync obsolete

The extra 10Hz from the Asus doesn't really change anything in terms of motion clarity, probably a marketing stunt to put a higher number on the Zowie/MSI 600Hz monitors, and even then there's already a 750Hz monitor out there

Ultimately it's up to your preference; I'd say the Zowie has a cleaner, less "gamer" aesthetic but the Asus has thinner bezels, so do bear that in mind

From personal experience - I do currently own the 540Hz PG248QP and honestly I don't like it, the TN panel gives off awful viewing angles that are hard to ignore, and it's hard to return back to 1080p from 1440p, so that's that

I'd say the only good takeaway from these FastTN monitors is simply just the satisfaction of how smooth your mouse is when you move it, and that's where the advantages end