Clearly this varies year to year. In 2006, you couldn't go anywhere in Boston without seeing/hearing/reading about the Hansons/Brooks partnership. They led the marathon coverage in the Globe, and it was as if no other company were even competing. So, these media darlings have an ebb and flow to them.
Interesting question from the original poster, though, asking what company best takes care of its pro's. Nike likely does over Brooks, but Brooks may take better care of the amateur athlete with products, promotions, abd sponsorships.