I am tuned on Shell 93. Thats what I usually fill up with. Tunewerks didn't ask me to try a different fuel and I can see no major issues with knock or fueling. My car regularly sees 208-215 climbing the hill when its hot outside. Still not seeing a bunch of negative corrections.
Been running Shell for the majority of the time I have owned the car. Not saying its better, just anecdotal evidence of my own experience. I have a Chevron right next to the Shell so I can pick either one.