No bezels is nice. However, I have three 24" ASUS monitors with probably around 1.5" of bezel between them, and it's honestly something you get used to. When gaming, you aren't really supposed to look directly at the other monitors anyway (there tends to be a lot of distortion to the sides), so the bezels aren't as big a deal as you might think. I would prefer to keep 5760x1080 over 3840x1440, but that might just me. The extra vertical space is nice, but not at the cost of almost 2000px in horizontal resolution.
Beyond that, the "ultra-wide" LG monitor isn't as good for a lot of productivity tasks. With three separate monitors, you have the advantage of the window manager allowing you to maximize or snap to multiple points instead of one giant one. So you can have three maximized windows with the click of a couple buttons, whereas on the LG monitor, you have to manually position them to achieve the same effect. If you use the "snap to side" feature found in Windows and at least some Linux WMs, you can quickly have six windows side-by-side filling three monitors. Finally, if you're watching a video in one monitor, maximizing it only fills that single monitor, leaving you two others to use in the meantime.