Back when I owned my NA Crossfire, I ran the test myself. With normal premium unleaded gas, I experienced a lower MPG but a more responsive throttle due to the higher octane rating. When I decided to chance it with 100% gasoline, I noticed a much better MPG due to it being a "clean gas" but also a less responsive throttle due to the lower octane rating. I liked the result of better MPG, but also missed my very responsive throttle so I continued to run 100% when available but with an octane booster every 3 or so tanks. After adding the octane booster I got both better MPG and my responsive throttle too.

TL;DR - With modern fuel injected engines, you can use either/or just fine without harming anything. Just adjust to your own liking! Good Luck!