3 years ago I bought this Asus G37JH gaming laptop. It's awesome still and can pretty much run anything at max graphics with little to no lag, but at the same time you can only have a couple of programs open without the whole computer starting to lag. (6gigs of ram/ i7 intel CPU) Desktops just have the ability to process a lot of things at the same time.
If I could get my money back and choose which kind of computer I got again, I would definitely go with a gaming desktop this time. They seem to be cheaper than gaming laptops atm too. It is nice to be able to move it around, but 95% time it's sitting on a table in the living room.