I dont know laptops too well, Im a workstation guy.
But basically you can get roughly the same specs for laptops as you can desktops now. Mobile stuff will always be slower and more prone to overheat and will always be more expensive. But if you look around you can find some good desktop replacements.
I would look for a i7 processor, minmum quad core with hyperthreading, at least 8GB of ram 16GB would be good if you use after effects, a dedicated graphics card from Nvidia preferably a 600 series. Hard drive wise having a HDD and SSD would be the best but may be very pricey.
If you go laptop make sure you get a cooling dock, and a spare battery is always nice.