This will completely depend on where you are and where the gas there is sourced from. No one single answer.
And yes, while "gas is gas" is sorta true, there is a lot of room in the specs to formulate and build the gas differently to allow for different refining processes and feedstocks.
In the Twin Cities, the American Lung Association used to test gas from the three major refiners product that dominated the area. They showed significant differences in the actual makeup and content of what was all sold as 87 octane E-10. That reflected the different recipe of feedstock and refining processes in use at the different refineries. In our area, you can count on Holiday gas being from Flint Hills refinery in Rosemount, MN. Superamerica gas will be from Northern Tier Refinery in St. Paul Park, MN. Everything else could be from either one of those two or from elsewhere via pipeline (Typically Tesoro in Mandan, ND or Calumet in Superior, WI (whose gasoline stinks to high heaven, as anyone who fuels in Northern MN can attest to).
You need to do your homework on your areas supply, not just assume that Brand X is the same everywhere. Its not.