Dell, generally, makes a higher quality system than does Acer. CPU performance is stronger on the Acer. Still, of these two choices, I would go with the Dell if it were up to me.
From my experience with my Samsung Freesync 4k display, just about any quality DisplayPort cable will meet your needs. You don't need to worry about flashy sales pitches and claimed "features".
For $55, you get a replacement card to use as a solid backup, or your could sell and get more for it. Seems like a small price for a win. I would go for it, if me.