Can only speak of my experience. My 2008 JKU is my daily driver. running 6speed manual with 5:13 gears and heavy 37" Toyo O/C mt. Last year I added a RIPP SC more for my trips to the NC mountains as I haul a 3800 lb camper but didnt need it for daily driving. I also run a sprint booster Throttle response module wchich gives that little extra kick. I couldnt be happier. my gas mileage is 14mpg in town and 16mpg on highway if I behave.
2008 JK Unlimited X
RIPP stage 2 supercharger, R/K xfactor 5.5" long arm coilover susp., 40"x13.5" G/Y kevlars, 17x9.5 Raceline beadlocks, EVO gussets and sleeves, Yukon chromoly shafts, Artec trusses, T/W drive shafts, Eaton lockers, G2 5:13 gears, ORFAB front bumper with smittybuilt 12000 winch, Body Armor rear bumper, ORFAB roll cage, Mastercraft Baja seats, SPOD