Woosdom :
I've had my asus rog laptop for about 5 yrs now and I play arma 3 all the time. I also play many other games and arma is really only one of the few that I can't play at max settings. So gaming on a laptop IMO is not as bad as people make it out to be. I have fun everywhere I travel gaming on it.
Agree, people who claim that are usually guys who play 12h per day at the minimum. Not that I want to be offensive or anything, but there's more in life than gaming. I like games, but it's not like I will play 12 hours straight. Anyway, I suggest you follow the steps above deciding your system:
1) If you're going to have your pc at house purely for gaming, get a console
2) If you're going to have your pc at house for multi purposes, and would mind a few fps, get a desktop
3) If you're going to travel or might think that it's a good idea to get a portable device just in case and want it to do anything included casual gaming and wouldn't mind a few fps, get a laptop
I, personally, wouldn't trade 10 fps for portability
Just as a reference for number one (1). Watch dogs is playable with a ps3/4 for 200$/500$. You would need atleast a 780 ti which costs 700$ alone, how much is the full system?