most jeeps come from the factory with a bit of a rake. like a pickup truck does. this is so when you load a bunch of friends and gear in the back, the vehicle levels out...and isn't bottoming out badly & dragging its arse around.
for some reason, some people want to eliminate this rake. that's what leveling kits are for. they eliminate the rake by raising the front end, making the vehicle sit more level....but now if you load gear in the back, the front end is pointing to the sky. if you don't carry gear or people, it might not be a problem for you.
a suspension lift replaces several suspension components. like springs, shocks and more. this lifts the whole vehicle up a specified amount. it can often include stiffer/taller springs in the front to eliminate some rake, and/or stiffer springs in the rear to compensate for towing or extra gear & heavy bumpers.
which one you want is up to you and the function your Jeep serves. do some homework and think about how your vehicle is used.
for example, after I installed a winch on my jeep, the front end dropped a little due to the extra weight. Consequently, I installed stiffer & longer springs in front to lift the front end back up where I want it. Similarly, I tow a trailer and carry a lot of gear in the back of my Jeep when go camping/hunting/etc, so I have fairly firm springs in the rear with AirLift airbags to help on-road stability when loaded, yet the airbags are adjustable such that it's not overly stiff unloaded.