Hi,
It's up to you - you would more than break even on both passes, but you get far greater value if you completed all your long distance itinerary within a week. That said, it would squeeze you more to do it all in 7 days. So if you normally have a fast travel pace, it would be easier for you, but if slower, it would be even harder on you.
You could compensate for not using the 14 day pass by taking the 1000 yen bus, and in Tokyo there is a good 2 or 3 day subway pass.
You didn't specifically mention it, but for Hiroshima you should also see Miyajima. You can see both Hiroshima and Miyajima with an early morning start. You can cover the Peace Park/Museum, castle, Shukkeien Garden and Okonomiyaki-mura, and then go down to take the JR ferry to the island. Aside from the Itsukushima Shrine with the giant "floating" torii, the Daishoin Temple is also a must-see place. There are several other pagodas and temples, and climbing Mt. Misen offers a fantastic view over the island and whole area.
You can also use the JR Pass on the loop bus for Hiroshima City.
If you have time, just a bit past Miyajima is Iwakuni with its iconic historical bridge and mountaintop castle.
Also don't skip Nara either. In Nara, the Todaiji Great Buddha is an extraordinary place, as well as many other historic temples, shrines and gardens in the area.
For Kyoto, try to time your visits to places to be more effective. The Fushimi Inari Shrine is open 24/7, so fitting it in early in the morning or evening allows you to add other places in between, and you can avoid a lot of the crowds at either time. The Honganji Temples open at the crack of dawn and are within walking distance of Kyoto Stn. so they are easy to fit in too.
Good luck.
