With backspacing, less is more. Less backspacing means your wheels are set further away from the chassis. This can be good for clearance, particularly if you've got fat tires. But it also causes more stress on the c's, hubs, ball joints and steering box because the center of the wheel is pushed further out from the pivot point.
Stay as close as you can to 4.5 unless you have a reason.
I'm a JKO Reject