Well, I'm not quite sure how many threads it takes to dj with, but I would imaging the new mbp would suffice, seeing how it has a higher turbo clock speed. Heck, its base speed is already 2.9ghz.
Also, the new mbp comes with a smaller screen (so saves on power usage) and a newer gpu, which also saves on power.
And finally, the new mpb has a brand new battery...and we all know its super expensive to change the battery in a mbp because they have to do it for you.
Plus, I believe the new mbp will come preinstalled with the newer OS? I could be wrong about this though...