Okay. First of all. What are you looking for. Pure SQ or Pure SPL or a little of each. Number Two. Do you only want JL Audio or Kicker? Sure they two very respectable brands and I personally love Kicker, but I also know that there are other brands out there that are superior, but at a higher price. Take, for example, MMAT, Digital Designs, Focal, Infinity, MBQuart, Audiobahn, as well as many more. Some are easier to find than others, some will deliver more SPL, and some will deliver more SQ. It is all personal opinion. And personally I take Kicker over all of them because of price, reliability, and their will and success in making high quality, high output, and durable subwoofers.
One thing not usually noted about kicker is their cone design. The Kicker Comp VRs and Kicker Comps are actually made out of a type of rubber. Now say one of your friends accidentally hits your subwoofer. Do you want him to be hitting a rubber cone or to be hitting the cones that are made out of a type of paper (usually used for higher SPL). I'm guessing you want him to hit the rubber cone because it will not even be phased. The paper cone... Well... You'll be returning that pretty soon. Anyway if you are looking for a subwoofer and you are really set on either JL Audio or Kicker, I personally would take the Kicker over JL Audio. You can see why about 20 posts down from this one. Look at all three of my posts.
And if you want me to give you a better idea of a good model to buy then please tell me what kind of budget you are on. I would go with the Kicker L7s because those should be arriving in a few weeks for me. Kicker L5s and L7s are unique in the way that they have a square shape as you might already know. This features gives it more cone area and is approximately the next step up so far a cone area. For example, the Kicker 10" L7 will have about as much cone area as normal round 12" speakers. I'm going to be getting the 15" L7 which is the equivalent of an 18" speaker. And more cone area means you move more air, which means you make more bass. Also when you are looking at subwoofers, their RMS wattage is much more important than their Peak wattage. But, tell me what your budget is and after doing a little research, tell me if you still think that Kicker is one of the companies that is right for you. Good luck.