Those guys are idiots, especially puling out that "gear chart" which shows just how clueless they are. That chart only shows the RPMs you'd see with the Overdrive shut off, not when you're driving on the highway with the Overdrive enabled. Your rpms will only be 69% of what their chart says. Really.
Don't even consider 4.56.
Edit: Confirm what size tires you're installing or running. With 33's, you definitely (!!!) need 4.88. Only if you had the 5-speed manual transmission would that shop be correct to recommend 4.56 gearing.
P.S. I used to work for the parent company of 4Wheel Parts and worked every day with 5-6 of their shops. I had to spend much my time educating the sales people and shop people about appropriate gear ratios, drivetrain angles, etc. Most of them drive big V8 pickup trucks that someone else built for them and they're clueless on the various differences on Wranglers that make ratios appropriate or inappropriate. To them, 4.56 is a outer-space stupid-low ratio... but then they don't know any better.
