Screw the portability. Get a PC. PC's have better hardware and can be upgraded, so you get more bang for your buck. Trust me. You'll never regret it.
Unless you really need something portable. Like if you are in college or have a job that requires a computer on the fly.
Also, keep in mind that laptops do not last long. They heat up very easily and most come equipped with mediocre hardware, aren't as modular as desktops, and are difficult to repair.
In conclusion, I definitely recommend getting a desktop PC. Only get a laptop if you actually need something portable.
AAAANND Alienware laptops don't suck. There's a dude called Ali-A on Youtube and he uses an Alienware laptop to play CoD BO2 and Ghosts, and it runs super smoothly.