laptops aren't the same as AIO system (or atleast laptops can be used on the move, AIO systems cannot)
by saying similar you mean having a desktop with laptop parts? (which to me makes no sense, just like imacs)
gaming on an AIO is like trying to win a 100m sprint by having 1 leg tied up... (it is possible ,yet makes no sense)
last time i checked AIO systems were also intended for average multimedia use at best.
lets not mix up two things that are alike but still got quite some significant advantages/disadvantages to either side.