Well, mine is an uneducated opinion, but seat of the pants feel and may not be all that useful. I recently changed my tires from 225/75-16's to 285/75-16's both running on the stock steel wheels and 3.73 gears. Can I tell there was a change, absolutely, plus the tires with 35 psi measure 31.75", I recalibrated with a procal and got the speedo within .6 mph. I have lost about 1.2 mpg, based upon the last 5 hour road trip that included a lot of slow hill driving on tight forest roads. The JK did great both on highway and offroad. Would 4.10's give me better acceleration, yes. Do I want to waste money on regearing for these tires no, especially since I plan in the long run to change out axle housings and gears in the future and putting on larger tires. But for now this is a DD and it isn't necessary to change them at this time. If I had 3.21 with 33" tires and wanted to change I would look for a set of 3.73's from someone who needed 4.10 or something smaller.

Must say Jeep Lab great write up. I like the other forums, but have been finding myself coming here for a lot of information lately.