You know the Great Rao had already written about the differences at this very site, I added them to the entry:
http://superman.nu/wiki/index.php/Earths_1_and_2You can read the full article here:
http://superman.nu/a/History/VersionI.phpand the quote:
Although the Earth 2 Superman is portrayed as being the character who appeared in the comics in the '40s, a number of differences exist. Perry White first appears as Clark Kent's boss in Superman #7 in December 1940, although the Earth 2 Superman supposedly never met Perry until after Clark Kent became editor of the Daily Star in the early '50s. The Daily Planet first appears in Superman #4, Spring 1940, with George Taylor as its editor. In another discrepancy the Earth 2 Luthor is portrayed as red headed, but the bald version of Luthor first appeared in Superman #10, June 1941.
The 1940s Superman also seems to have had a power that the Earth 2 Superman lacks, the ability to use his "super muscular control" to contort his face into any form of disguise that he wishes. This power was first used in Superman #18 and continued to be used through the end of 1947.