To be honest, the main thing that I would pay a lot of attention to is to make sure that whatever graphic card you take, it has the GPU Compute Capability 1.3 or above. If it doesn't, you'll be stuck without having the possibility to use GPU processing (which is becoming quite trendy). You should also consider taking an Intel processor ( reasons here and references therein ). For all the rest, as long as you have 64 bits hardware and OS, and 8GB RAM or more, you won't be too stuck I guess.
To be honest, after these items, what matters the most for me in a laptop is the keyboard and the screen ;-) [I can cope with a small processor, but not with a headache-generating screen or a clicking keyboard]. About the overall power, I have a powerful computation server in my office, but I find my moderately powerful laptop to be a good test for my algorithms .. in the sense that most often if "things" don't run on a laptop, it's because of a bad design. So, as far as I am concerned, it is actually quite rare that what I design legitimately requires the power of the server or of an over-boosted laptop, and I am happy with a decent enough laptop even if it's not a killer.