Which Part of Tokyo to stay in?

Hi all - Me and a friend are in Tokyo from the 6th to the 11th and can't decide which area to stay in. As we will be sampling a lot of the nightlife it is important to for us to be able to get back to our Hotel late at night and i have heard that Taxis in Tokyo can be expensive. And assuming that the best nighltife and live music / Indie/ Funk/ Soul etc can be found in the Shibuya and Shinjuku areas how far away could we realistically stay without having too much trouble finding our way back to our Hotel??

Thanks

Obviously, a hotel in the Shibuya or Shinjuku area would be most suitable. You can walk between Shibuya and Shinjuku in about an hour.

The best area for the nightlife is Roppongi. Roppongi is an expensive area, but the B Roppongi Hotel has reasonable rates.