Question about ASUS ROG Swift PG278QR

I would have difficulties there too :)
So: Both are equipped with a TN panel, you are sure you don't want an IPS panel? TN panels are good! But they have a worse viewing angle than IPS panels and display blacks worse. But they are more solid and cheaper and have a better response time -> good for shooters!
The Asus has 165hz, the Dell only 144hz -> but 144 hz should be completely sufficient. You probably won't be able to experience 165hz with a 2k resolution.

Dell has made many good monitors, so you won't be making a mistake if you buy the Dell.

Go for the one you like better in terms of looks, both are good!