Finally got my GZ to 50, I am playing on ps3.
I have come to realize 2 things I really hate about 2 as compared to one.
-27 inventory slots instead of 42
-Vehicles have problems killing things 20 levels lower than you by just running them over.
Oh and the fact that with a 30k shield and being level 45, level 34 baddies can still nearly kill you.