Which sub woofer would hit harder?

It is a very difficult question to answer with the information that you provided. You say that you will provide 1000 rms to the lanzar and 750 rms to the Kicker. Does this mean that you you will be buying the amplifier based on which subwoofer you get. If you already have the amplifier than you will have a higher output from the kicker sub because a 2 ohm DVC will give you 1 ohm in parallel and the lanzar will give you 2 ohms (assuming your amp can take a 1ohm load). If your looking for sound quality, your best bet would be with the kicker sub. As for the which one would hit harder, it depends on many factors. The enclosure will have a big impact. A ported box if tuned properly can sound just as good as a sealed box. It will sound louder, but it will be larger. Some people will disagree with me on this one but its true. You need to check on the subwoofer manual to see what size box they recommend and if it fits in your car. Once you have the right size box, the next thing you have is power. If you are providing 750 rms to the kicker and 1000rms to the lanzar (assuming that they are rated for this amount of power), then the lanzar sub would have the advantage and should be able to hit harder.