Some armor will be needed if you really use your Jeep. We are a big fan of steel belly pans but otherwise, if the Jeep is a budget build or going to be ground into the rocks daily, go with steel. If the budget isn’t a big deal or weight is a concern, go aluminum. The aluminum will almost always be about 50 percent more expensive and is usually about one third to one half the weight of the steel. With the appropriate primer, getting paint to stick to it isn’t a problem, so it just comes down to how hard you are beating your Jeep and how deep your wallet is.