You'd have to understand what the 80+ is to get a better understanding on your question. But for simplicity, the higher grades are slightly more efficient in power conversion from 120/240v to 12v/5v/3.3v. Also, the higher grades have better ripple, important for extreme OC of ram, cpu and multiple gpus. Extreme. If you are running an average, balanced, even higher-end OC pc, bronze is fine, gold if you are starting to push limits, platinum if you are at the limits and titanium if you are the 0.01% who just plain want to remake limits.
Is it worth it? I'll put my Seasonic M12-II 520w 80+Bronze up against any Corsair Gold except some HX, AX (also made by Seasonic so a moot point) and dare them to beat me for output, ripple, quality of build, quality of components or even reliability.
It's not what the psu claims that's all that important, but who is doin the claiming.