I have a theory about what keeps drawing them together, despite their many differences.
Bruce Wayne is very similar to Superman. Handsome, lionized, a "protector" of the city, albeit only in a financial selnse many women attracted to him. Bruce Wayne and Superman have a lot more in common than Superman/Batman.
On the other hand, Batman is an investigator, and used to being ...disturbing in appearance. Clark Kent is an ace reporter, and often used to ferretting out secrets and knowing more than he lets on, and yet, not lionized for his appearance---although not feared, but rather mocked.
Bruce Wayne/Superman are alike...
Batman/Clark Kent are alike...
Each's costumed identity can find points of reference with the other's civilian identity, and vice versa.
---Al
Hmmm, interesting idea.
Clark Kent's skill as an investigative reporter, however, has been historically underplayed, and with rather good reason, though: 1) if Superman was really good at his job, he wouldn't be a put-upon loser, 2) being a great reporter is really Lois's thing, 3) Clark Kent is far too "mildmannered" to be any good at all at being a hardhitting, question asking investigative reporter.
Though Bruce Wayne as a millionaire was always shown to be a responsible, Tony Stark type whose employees are probably very well provided for. Clark Kent as a crusading reporter, probably has a sense of social justice that is deeply repressed to keep his Clark Kent cover inoffensive and meek. Why be a reporter, and not, say, an air traffic controller?
Incidentally, Al Shroeder, I just read your incredible Wold-Newton Geneology for Captain America, and it was magnificently conceived. The most stylish one was the link to that landscape painter named "Rogers." I especially like the idea that Jonny from the Fab 5 was responsible for Steve's recruitment for the Super Soldier Program. It makes Steve's selection less arbitrary.
And keep up the good work on MINDMISTRESS. It's the first, and only Webcomic I read as a standard.