This area is not actually my division but because I'm a petrolhead I talk with the automotive guys very very frequently. Our star performers are fuel additives, antifreeze/coolants and brake fluid all for high end applications.
I do get swayed by this and the fact I've been in motorsport/motortrade for 30+ years.
The thing that really convinced me (although I didn't need much convincing) apart from the science I know from work was. We once did an engine repair on a BMW 530d which had covered 70,000 miles. The owner was a real scrooge and it had been run all its life on a particular brand of supermarket fuel. The head was so gummed up with deposits it was unreal as was the EGR valve etc.. Then my nephews BMW 525d decided to ingest a swirl flap so we had to strip the engine, this car had covered 127,000 miles and had run all its life on Shell V Power diesel. The difference was night and day this head was clean as a whistle no deposits at all in fact no trace of black gunge.
I'm not saying this was all down to the fuel as I suspect the first BMW had missed some services and had the wrong oil used at some stage but even so the difference was striking
So people who say supermarket fuel is as good as branded fuel let them believe that, sure the base spec is the same but the additive packages are way different.
Sorry to digress but to answer your question Shell for me or if I can't find Shell then Texaco their Techron additive package is really very good.
Very rare you get poor fuel these days and has been said it's usually down to tank management or fuel with low additive levels that's been sat in the tank for ages.
Below are independent test results on a Golf GTi to assess performance of various fuels in terms of power
Bp unleaded 236.1 bhp
Asda unleaded 235.8bhp
Bp ultimate 236.7bhp
Esso supreme 240.5bhp
Shell V power 240.9bhp
Results are an average of 5 dyno runs and are statistically solid.
Interesting which one produces the lowest BHP
I wonder why