Tom's Hardware did the work and Extreme Tech summarized it. They both conclude: There is no comparison -- AMD Freesync wins this one.

Quote
FreeSync, G-Sync Go Head to Head in New Monitor Comparison

[Tested] two new monitors from the same company — AOC — head to head. The AOC Agon AG241QG is a new 24-inch G-Sync panel, while the AOC Agon AG241QX is a FreeSync panel.

They differ in two significant ways: The QG [Nvidia] G-Sync panel costs $600, while the [AMD=Freesync] QX is $320, and the [AMD-Freesync] QX is the absolute and clear winner of the comparison.

the QX panel proved to be far better calibrated out of the box. It also offers a brighter white, deeper black, vastly better contrast ratios, and a much better default experience

As far as FreeSync versus G-Sync performance, the two were identical. No visual differences could be detected in testing. The dynamic range on the QX panel is nearly 2x larger than the QG


Tom's Hardware Article

This is only one test and the supposedly identical monitors may have had internal differences (besides Sync). However, the AMD-FreeSync panel cost far less -- implying that hidden advantages are less likely.

Attached Files Which Monitors Perform Better - Tom's Hardware.png

Sapphire Pulse RX7900XTX, 3 monitors = 23P (1080p) + SAMSUNG 32" Odyssey Neo G7 1000R curve (4K/2160p) + 23P (1080p), AMD R9-7950X (ARCTIC Liquid Freezer II 420), 64GB RAM@6.0GHz, Gigabyte X670E AORUS MASTER MB, (4x M.2 SSD + 2xSSD + 2xHD) = ~52TB storage, EVGA 1600W PSU, Phanteks Enthoo Pro Full Tower, ASUS RT-AX89X 6000Mbps WiFi router, VKB Gladiator WW2 Stick, Pedals, G.Skill RGB KB, AORUS Thunder M7 Mouse, W11 Pro