JL, def., unless you think havin a lot of woofers are cool. The kicker cvr's are good, but they don't compare to the w6's.
ohms are very important. It tells you how much resistance your amplifier is encountering while trying to power subs. In almost all cases the lower the ohm value the more power from the amp. but there is much more to pay attention to in that area.
well it all depends on what you would call better. is better so loud that it blurrs your vision or is better when you put on your favorite song and you hear every bass detail to perfection? that is the difference between high SPL and great SQ. I am not saying the Kickers willl blurr your vision due to high SPL but they will get louder then 2 jl12w6's because of surface area alone. The JL's will sound much much better though. It also depends on what type of enclosure you are talking about and how much power. you can compare to subs but when you throw in type of enclosure and power and vehicle it really changes things around.