I run the 3.5" on the wifes street JKU. They are tighter springs and it rides rougher than Her offroad JKU with a 4" Teraflex. It is not a bad run though. Rides about like a stock LJ. Go with a full suspension lift and kill the coil boosters.
http://www.roughcountry.com/jeep_jk_3-seriesII.html
Or go with the 4" lift.
http://www.roughcountry.com/jeep_jk_4.html
Also, you can call them direct and they will usually give you discount on price. Tell them you were looking at the cheaper lift but really want the other, are there any sales n it or discounts? He will usually give you one.