The two types of setup are completely different. A 3 monitor setup doesnt give you clarity, it gives you field of view. 5760x1080 doesnt look any sharper than just 1080 since you're spreading it out over 3 screens, it just lets you see more when playing games (adds peripheral vision kinda). When not gaming 3 screens is great for multi-tasking. The bezels arent intrusive once you get use to the setup and realize how it works. You shouldnt be turning your head to look at the two side screens in a 3 screen setup when gaming. If you want to see something thats on the side screen you would turn your view in game as if you were turning your head.
Compare this to a large monitor and you have all the pixels on one screen so the super large with higher resolution (4k) will give you a much clearer image than 3x1080p, but the field of view will be much smaller.
As far as which is better, this all depends on the game, task, or user. I personally run a 3+1 setup so can have the best of both worlds. For flight sims and other games like them I would NEVER go back to playing on one screen. The level of emersion and situational awareness the extra screens ads is perfect for simulators. Other games like Diablo 3 there really isnt much point in using 3 screens and you're better off with 1 higher resolution screen.