I use Chevron myself, mainly because of the Techron in it, for keeping my injectors and valves clean. It's also a Tier 3 fuel. I've used Shell on occasion, when no Chevron station is around. Sadly, I don't know of any gas stations here in the NW which sell fuel w/o any ethanol in it. Ethanol is a complete waste of money. It kills both your mileage and performance, and when it comes to the environment, taking into account the pollution created in it's manufacture, the advantage(s) is canceled out.Do what makes you feel better, but this is mostly a placebo effect. Premium gas and reglar both have a required level of detergents. Shell will advertise additional detergents, but look into it and you will find little support for using the additional additives. The only real benefit to your fuel choice is the ethanol free part.
While I don't think it is a concern for the XV, I know for a fact that the quality of fuel for the same brand and same octane level can vary by gas station. I used to swear by Shell 93 octane in my Focus ST. I moved to a different city and my data logs showed the car was pulling a little timing. Switched to BP 93 octane and problem solved. Did a little reading and found out from reputable tuners that quality variations like this exist.
Paying a Premium for High Octane Gasoline? | Consumer Information
I not only read that Techron is the best to use, when keeping your fuel system clean, but talked to mechanics, including those who work for Porsche and BMW, who said likewise. I haven't heard anyone have anything bad to say about using Techron, or say that it doesn't work. As for what Shell uses, I can't comment there, other than they do use detergents.
On the other hand, I won't ever use Arco. I've known people who used nothing but Arco, and had issues w/their Injectors eventually giving them problems. After having them cleaned, everything was back to normal. I've told them to stay away from Arco. From what I've heard, Arco has either no detergents in it, or very little, which is what makes it cheaper to buy.