I had a gaming laptop for 4 years. Trust me, it's a needless hassle.
-They're not easy to upgrade whereas a desktop you can build yourself and pop open the case to swap out video cards or RAM.
-If you're going to have it on your lap, it will melt your balls off with the heat produced by a nice processor/video card in such a small and poorly cooled case. If youre going to put it on a desk, then just get a laptop. You won't wanna play an online fps with a laptop anyways.
-One problem I always had with gaming sessions on my laptop was that after a while it would start to overheat, which would drop frames per second, which basically frick you over for any shooter.
EDIT: I've got friends that built their own from newegg.com and friends that weren't comfortable so they paid a little more and got one built for them from ibuypower.com
Either way is a safe bet if you know what components you want.
This post was edited on 8/8 at 9:45 pm