Depends on what you want to do. Are you going to 4" lift and 35s for the look, or are you going to use it in the boonies? If you are going to drive it mostly on the highway, you want to keep the mileage. If you are going in the boonies, you need the grunt.
Of course, if you put it in LO, you have 5.46:1 right now. :-)
Here's an RPM chart of ratios and tire sizes for your planning.
http://www.southwestpowersports.com/GEARCHANGE.HTML
You are not even on the chart, currently, but you can look up under 5.38:1 and divide by 2. Don't forget, that is for 1:1 through the transmission, which is in 3rd gear. For OD rpms, multiply by .7.