Reading this inspired me to do a test. I'd take the last compilation I'd burned of music download from the web, and check how many of the tracks were actually available from each of the new services.
Unfortunatly I can't. None of the services seems to offer searchable catalogues of the artists they stock. This seems extraordinary. Surely the biggest selling point the service could have is that you could check whether your 10 - 15 favourite bands were available?
(Rhapsody has it's catalogue online ... but only in browsable pages of 40. Why? And no links to artist's details to check this is the artist you're looking for if you're unsure of the name. No listener recommendations. Oh, and they don't do Momus, Current 93, The Cardiacs, Bally Sagoo)
Conclusion. Amazon will win the online music retail space.