Better connection, quicker reflexes and mostly the ability to play with the WiiMote.
Something i've never been able to conquer.
the one thing they now how to do with perfection, and something i'm trying to improve on
is the kill and run. (Wondering what i mean?)
--> When you kill some1 in a gun batlle you often get killed as well when your line of sights are a match.
That is when you linger to long after putting enough bullets for the kill.
So basically you need to change your trajectory the moment you poured in enough bullets to secure your kill.
Ofcourse if you change your trajectory too soon, the other one survives...
Also they know their running lines to perfection.