I do not know anything else but that Shell and Chevron have good as overall and if your car is fine with a specific octane to just go with that. 

The reason Chevron and Shell are the best comes down to an additive called Techron. Essentially, Chevron uses it in their gas blends to help clean the engine as it goes through. Shell does not use Techron but has an additive they call Shell Nitro that does the same thing. Those two are the strongest cleaning additives in the industry.

Of course, if you want you can always burn whatever gas you want and add a bottle of Techron every other tank as they do sell it in auto parts stores. But it is much cheaper to just buy it as your regular fuel. I only ever burn Shell gasoline in my cars and believe it or not I can tell you the difference between a Shell fueled motor at 100k miles and other brands. On the Shell fueled engines, I've seen LS1 and LS2 motors still have the hatchmarks showing clearly in the cylinder walls at 150k miles. 

It is more expensive. Generally Shell is the most expensive fuel around. But from what I have seen, you do get your money's worth in the long run.

I've always bought whatever is convenient