The 520 chain isn't better, same pitch, but it is narrower which allows the use of an o-ring chain on your CB550 with room to spare. You'll need to switch to narrower sprockets to suit. If your chain is finished then you should change sprockets anyway. I had a machinist reduce the width of a stock front and bought a rear blank from Sprocket Specialists and machined the centre hole to fit. The conversion is narrower, lighter and plenty strong enough. Check out the 200hp plus superbikes at your local race track, most use 520 chain.
Just another option.