As much as I love their laptops, I value power more than mobility, because as a rule when I'm "on the go" I don't have time for gaming anyways.
Although I'd love to get myself a M11x for use at university!
I use my m17x for work and play so I like the laptop but I also have a desktop and it's not an AW but the laptops are just so awesome and well portability is a good thing considering my desktop case alone is 30lbs so if you wanna swing over to a buddies house and hit up a night of brews and baddies than the laptop is the way to go.
On paper, the alienware desktops perform leagues ahead of any laptop, but for practical purposes you can just as easily max out settings on a m17x or m18x for almost any game out there. In the end I prefer the mobility of a laptop/desktop replacement.
I went with the m17x. I would love to have spent money to build my own rig and deck things out, but I had to make the call. In the end, I have to have something portable. I need the ability to take my system to many placed, from family's houses, to road trips, to clients locations (for my IT work), and so portability is a must. I have my tablet and phone, but my tech world is laptop centered. Not to mention I do a lot of gaming, and keep tons and tons of rulebooks and everything on my system.
if i was going to get a desktop i would much rather just build one. if im going to buy an alienware im gonna get a laptop. thats why i got a m17x. i think alienware has some of the best laptops on the market but i don't see much advantage of getting the desktop unless its the bragging rights of owning an alienware desktop.
As Far As For Choices Between Different Hardware That Can Be Loaded... Desktop Is Always The Winner You Can Build Your Own Killer Rig For Gaming....Gaming Laptops Like from Alienware, Asus & Razer Are Not Bad Either... I Love My m14x