While some guys you will meet on the trail talk about installing a lift kit as a simple procedure, it is not something you should enter into lightly. While it is not terribly complicated to do, the implications can completely change the dynamics of your Jeep and so it is critical that you do it with a plan in mind. When done correctly, your Jeep will look cooler, offer better visibility and perform better when tackling obstacles on the trail.
The benefits of installing a Jeep lift kit are pretty easy to understand. However, by raising your vehicle up a few inches you are shifting the center of gravity, air flow dynamics, and most likely are voiding any manufacturer's warrantee. While the warrantee is something most Jeep owners could care less about, raising the center of gravity means that you now have an increased roll-over risk on steep trails. On the highway, this also means that you can't take corners as fast.
Additionally, since most people will be installing bigger tires along with any lift kit upgrade, you will see significant reduction in fuel economy. Your Jeep will also be more challenging to get in and out of since it is that much higher off the ground now.
Despite those words of caution, most Jeep owners will at least consider adding a lift kit. There are two different options to consider - a lift kit (simply raises the body higher off the frame) and a lift kit with suspension where you replace the shocks, struts, and some, most or all elements of the suspension system to create an overall completely different ride experience. While the basic lift kit is a great option for those that just want a basic improvement, most guys will ultimately feel compelled to go "all in" and create a highly custom look and feel that matches their personality and drive style.
It Just Looks Cool
The "cool factor" simply can't be dismissed. Your Jeep will have a taller and more aggressive look. This looks cool and immediately sets yours apart from any stock Jeep on the trail. Additionally, when coupled with lift kits from specific brands you have that association with being a more serious off-road guy. While there are a lot of upgrades that you can add to your jeep to make it look cool, a lift kit is one of the first that most guys will consider.
Raising the Jeep up a few extra inches allows you to see further. This means you can potentially see obstacles further out than your stock Jeep would allow. Additionally since you are looking at closer obstacles from a higher angle, you can often get a better impression of depth and angle. This will allow you to formulate a better strategy to overcome the obstacle.
More Aggressive Tire Options Offering Improved Clearance
While a lift kit by itself will not offer any improvement to ground clearance, new tires can. By raising the wheels up you now have the opportunity to install bigger and more aggressive tires. This additional height will further improve your visibility benefit as well as ability to tackle tough obstacles since you now have more clearance and better treads.
Improved Towing Ability
By improving the lift and suspension, you can now reduce the squatting caused by standard suspension under heavy loads. While this is probably more important for guys looking at lift kits and suspension upgrades for their trucks ... Jeep guys tow sometimes too.