I was here in January for a transit and in Conrad Osaka last week - Havent stayed here for a LONG time but I stayed at the one in Osaka a few times the last 2 years. In short, I very much side with [MENTION=83541]Ross0[/MENTION] (and his report. His summary for Conrad Osaka is here.)

The only good part for the Tokyo for me was that I've gotten a suite (because I asked). I've had a Executive Twin in Osaka on my first stay and Executive Double this time - the 2 times last year I didnt get one but one time it was full because of corp functions.

The breakfast was MUCHHHHH better at the Osaka. better spread, more stations so there's less congestion, slightly modern take on japanese breakfast (but I see the spread seem to have dropped - I hope this is because of the busy times and is not permanent). PS: I see his comment on the spread of chinese food in Conrad Tokyo - i dont know how it taste, i dont care if they existed. If i wanted chinese food I would go to china, not Japan. However, for what I've tried at both hotels, Conrad Osaka served a good fried rice (with dried seafood, that wasn't explicitly marketed as such) and Conrad Tokyo served a good fried e-fu noodle (with mixed mushrooms).
Obviously the room in Osaka is newer.
Lounge: better general spread in Osaka. I've never made the evening cocktail hour a meal in Japan but it has nicer offerings. The Tokyo lounge seems like the nicer airline lounges with a few hot plates. kind of out of place! However, beers in Tokyo (Coedo) is better than Osaka (Kirin and Heineken).

Didnt use the gym/spa of the Conrad Tokyo, but the one in Osaka is good. Very good.