It all depends on current coils and replacement coils. Just because you get a set of springs off a JKU and put it on a JK doesn't mean you are getting stiffer set. In general, JKU's tend to have stiffer coils but not always. Jeeps seems to have a no set coils for a certain Jeep. At least that anyone can figure out. You need to get the number off the coils, should have a white tag on the coils with a number on it. The last two numbers are the coils spring rating. The front should be from 13-19 and the rear should be from 53-60. The larger the number the stiffer the springs. Usually get around .3" to .5" for each number you go up
Saying that, I had a set of 15/54 coils on my JK and ordered from Mopar.com a set of 19/60's and got around 1.5" up front (Had a heavy aftermarket bumper added) and 2" in rear. Added a set of 1" Teraflex coil spacers up front to level out for 2.5" up front in the end before eventually going to a 3" lift.