7 or 14 Day Rail Pass

I am travelling to Japan from Australia with my friend. We arrive in Tokyo and will be staying in Tokyo for 10 nights, we will then travel to Osaka and spend 5 nights there and then spend 2 nights in Kyoto on the way back to Tokyo. We then fly back to Australia after our final two days in Tokyo. Would it be more economical to buy a 7 day JR pass or a 14 day one? I thought about just getting a 7 day pass for our trip to Osaka/Kyoto. But can you use the JR rail pass much around Tokyo or is it more for long distant travels. While in Tokyo we would probably just be using the Odakyu, Keio and Yamanote train lines the most. Any help would be greatly appreciated.