As always, break it down to the minimum facts:
There is a legal standard that all fuels have to meet to be classed as Super/Premium/97RON or higher. This is a pretty tough standard to meet, so you can guarantee that the fuel is of a certain quality. Every single 97RON+ fuel on sale in the UK today meets this standard as a minimum, and anything above that you're arguing tiny percentages of betterness. As long as whatever you put in your car meets the RON minimum for your vehicle, there's zero evidence to prove either way that one is better than another. If there was proper evidence, then Shell/BP/Esso would be screaming it from the rooftops.
They're not. So there isn't. Just drive your damn cars and enjoy them