ANOTHER ALTERNATE EARTH! Why wasn't THIS one shown in COIE? ;-)
probably the same reason why theres no Earth-E or Earth-B in it! imagine the story with three very slightly different supermans hanging around....
then again, im taking a joke too far
i just found it odd that they first appeared in the strip rather than the comic, you think they would start out in the comic (which would be seen as the definitive medium for superman i would think) and then get recycled for the strips
and yes, bizzaro and brainiaic are more scary, and the metallo seems more realistic and destressed, unlike in the comics where he takes it with ease "ooh ive got a robot body now, back to the life of crime!"