I really think it depends on the authors and how they like to write. I'm strong on plot and character, but my descriptions need work. I might want to find an author who prefers to work on the descriptive end and go from there. Another possibility is for the 2 authors to work on the plot outline together and then take the sections that most interest them and start doing them, then exchanging after the first draft to blend the styles together, as well as make sure the minor details are consistant. I did hear about 2 well known mystery authors who co-wrote a book, where one did the first half, and the other the second half. I don't remember the review of the book (nor did I read the book) but one of the two authors said it was the most miserable experience of his life. He grew to hate the other author by the end of the book. As for creative differences, I think it depends on how the collaboration was formed. If one author is the primary writer, then most of the time they should probably have final say. If one is acting more as the impartial editor, then maybe they should have more say. You even may want to consider a third party, such as a mutual friend, to look at the disagreement and give their opinion. Hope it helps! (And any hints on whom you're collaborating with, what you're writing, and how long before we see it in print?)