Where I live Shell is the only chain that does not add ethanol to its 91 octane so Shell is what I buy.
Ethanol is just plain bad for your engine so if you can find a chain that has no/low ethanol content then I would stick to them.
Straight lines are for fast cars...turns are for fast drivers
'04 M3 - track
'06 650i Cab - daily driver
'02 Highlander - kid hauler
'01 330Ci - winter beater