DannyD2 I'm leaning towards keeping the one with the DCN panel. It feels really easy on the eyes.
Yup, you're correct, definitely keep DCN instead.
M2 TB Pro "FMX" panel (the one on my second M2 TB) looks sharper and more uniform "at first" with "slightly" more strain, but the longer you use it, the nausea and lightheadedness REALLY begins to get intense. It took a few days for this to really hit.
On the other hand, never noticed any pain like that at all on my first M2 TB Pro panel, even after using that one for basically the same amount of days too! My first M2 TB felt more comfortable like your DCN panel, no nausea.
(The reason I returned my first M2 TB is that uniformity was REALLY bad on mine, the right half of the screen straight up showed whites as light greens instead. Didn't have enough color accuracy for design work. But despite that [really obvious] uniformity defect, that first panel felt much more relaxing and didn't cause ANYWHERE near as much strain! Seems like no one else has got a uniformity defect THAT bad though which is great to hear LOL)
The best way to compare DCN and FMX is to set them both to low hardware backlight level. The problem I had at this point on my FMX is that it looked like it was "still too bright" even though it was dimmer, like turning down backlight didn't make colors more relaxing "like it's supposed to".
On the other hand, I remember my first panel actually "properly" getting dim (unlike FMX).
Even at the minimum backlight level possible, the FMX panel still felt like "I wanted to turn it down more" or "it's still too saturated" which is when I finally noticed what felt off about the FMX panel.
FMX also has much more glare and "text glow" than other M2 TB Pro panel types IMO, at least on my unit.
Keep DCN. Return FMX!
Both me and madmozg have had FMX panels that caused the same really bad nausea for both of us, so I'd say that it's very likely all FMX panels are bad for sensitive users.