I've been pretty much using Chevron in all my Infiniti vehicles and the JX and it seems to be an excellent fuel. I haven't used Shell in decades because it made one of my vehicles ping. I'm sure today's Shell is high quality. Here in Washington State I find Chevron to run several cents cheaper than Shell.
Yes there is a difference, Chevron and Shell gas are what they call tier 3 gas. It has more detergents in it. You can't tell the difference while driving, but if you did a check for carbon deposits using cheaper gas instead of the tier 3 gas it would be much more significant. To combat this you can just use a engine cleaner, such as sea foam; which is also what I recommend for this type of product. You can pick one up at mostly all car stores, such as discount advanced auto parts.
After many miles (50,000+) of using cheaper gas the deposits will build, but can be cleaned.
If you want to just make sure you engine is clean use chevron, or shell, but really overall you will probably never notice a difference if you're not very mechanically inclined.