I don't think it is a universal truth that Shell premium gasoline is better than the rest. There are regional differences due to blending, for one thing. Also, there is more to consider than deposit control, although that is one thing to consider. I do like Shell's advertisements, especially the ones with Ferrari racing cars, but that doesn't sway my purchases. The issue with deposit control is that once you have sufficient and effective enough additives to prevent deposits building up on valves, there is no advantage to using more or better additives.

I tend to use Chevron gasoline due to their higher AKI (in my region), and their reduced use of ethanol. I can get 94 AKI with no ethanol, only at Chevron. That matters as much to me as deposit control additives. I use Shell when travelling. I also use Esso fairly regularly. All of those have essentially equivalent deposit control additives, and are name brand stations that tend to have good controls in place, reasonable quality control, and so on.

Full disclosure: I used to work with Chevron (in an independent distributor, not production); I have a family member working at Esso in distribution; and my former company used Shell as a supplier, rebranding their products to sell under our house brand. I know that they are all pretty much the same, even beyond the fact that they share bulk petroleum between them.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue