By contrast the western battlesuit portrayal is very calculating, cold, and contemplated.  I think there is a deep psychological difference between eastern and western minds.

I think you are correct but in both situations the mech matters.  Yes in the Japanese portrayal the mech becomes part of the character (the pilot) but going further the character becomes part of the mech as well.  We already know mechs to be mindless machines without their pilots so while the mechs appear to be acting on behalf of a character we care about and becoming a similar character likewise the plot shows that the pilot becomes partly mech to convey the inhuman nature of the battlefield.  Their (pilots) thinking becomes problematic even while their reflexes become superhuman.  In both cases though the pilot being hidden within the machine and his potential is interconnected with the instrument of his use.  I wouldn't hold anything against either portrayal but it is interesting to see the cultural differences.  In the Japanese the berserker mode is seen from the viewpoint of the pilot.  His heavy breathing, his rage and sometimes screams.  The mech itself is forced to operate under such conditions and goes haywire reacting instinctively to the pilot's wishes and unleashes bizarre capabilities.  In the western mech the bond is more like a friendship.  It's almost as if the western mech is trying to get as far as possible from its portrayal otherwise as a mechanical slave, which technically speaking it is if you choose to anthropomorphosize.  There is no berserker mode, rather it is the pilot's thinking that the mech is like a friend, or brother in arms on the battlefield.