Of those two, the Acer.
The thing that everyone overlooks is bezel thickness. Get the measurements of the bezel off the newegg listing and then double it. That’s how thick the black line in-between the images will be. It might not seem like much now but wait till your gaming on it, it’s annoying.
The Acer has a thinner bezel. Also make sure your monitor has a vesa mount. if you ever want to put them on a three monitor stand, they will need vesa mounts. The Acer has one. The Dell doesn't appear to.