Hi Jim, I guess its a bit like the oil preference question.. Based on peoples foibles and prejudices, rather than hard scientific evidence there will be as many differing opinions as there are posters....
Having said that i offer my tuppence worth... I admit right off i run a normal carbed bike with medium compression that would probably run on paraffin if forced, but strangely i fill with the most expensive petrol that i wouldn't even put in my alfa.
I've convinced myself i'm trying to keep away from Ethanol additive, which i'm sure is having a detrimental effect on carb inlet hoses and orings generally.
Even the fuel pipe from the tank seems to have hardened... That was due to using Tesco momentum 99 ron which if u look on their web site contains 5% ethanol...
So, have been running for a while now on Shell V Power which as far as i can find has no ethanol... Yes expensive but only costs £20.00 per tank and lasts me a fortnight..
For EFI's i would think it probable that good branded fuel with cleaning additives would be best for injectors etc, and electronically controlled mixtures but what effect additives would have on lamda sensors i'm not sure.. However keep away from ethanol for as long as possible, if only to preserve your petrol tank from water damage...
I've wittered enough i think... regards gwilly. Shell V Power
http://en.wikipedia.org/wiki/Shell_V-Power