There are differences. as ginrai said above, the clear plastic on hasbro's is smokey, and the takara one has crystal clear plastic. the facial paint applications are different as well.
Perhaps but Digital Toys Inc. has the Taraka version. the clear or smokey parts aren't a problem cause I'll paint those anyways,I was just wondering if the joints of one may be better or worse then the other.
every joint except the hands, neck, waist, elbow and knee rotation on unicron are ratchet joints, so loose joints are impossible unless it's broken.