In all seriousness, almost any laptop will do the job you need. Running CAD from a laptop is crappy at the best of times, and won't make a blind bit of difference what laptop you run it on (within reason).
A desktop would be preferable if not just for more screen real estate. UNLESS...
You are loaded in which case you should take a look at the new Alienware M18x. It is a beautiful peace of hardware with a big screen and a graphics card (or two if you feel so inclined) to power a big *** monitor alongside the generous 18.4" of the laptop itself! One problem. You'll probably spending a lot of time at the chiropractor with back problems since it weighs a more than hefty 5.41KG. And incidentally a visit to your bank manager wouldn't be a bad move either with prices starting at an eye watering £1698.99