It is not at all worth it to me.

You might not need a JR Pass at all. It depends on how many days you will spend from the day you leave Gora to the day you arrive in Kyoto.

If that period is 7 days (sounds like it would be more) then maybe you can get 7-day pass. I took a look at the ordinary fares and it might save a little bit but it is very close to break even using the pass vs just paying the regular fare.

Are you traveling from Takayama to Miyajima (i.e. are the stops listed in order, gotta ask)?

Without a JR Pass you could buy a Nozomi shinkansen ticket to Hiroshima with no change of trains. Using a JR Pass would require a change. The change is not a big deal but if the pass isn't saving much (actually might cost a bit more) then taking the Nozomi for that leg tips the balance, I think. Same might apply for the day you travel to Kyoto.

Takayama to Miyajima is a long haul, 6.5 hours then walk to the ferry, the ferry, and to your lodging. I did this trip once in the opposite direction and won't do it again.

I've had both Green and regular passes in japan. I don't find enough difference in the cars to warrant the difference in price. Both have nice wide seats, enough space for my luggage, clean windows, and the same on-time records.

I made a mistake and forgot the travel day to Takayama. The 7-day pass would save about ¥10,000 vs buying the tickets. Ordinary cars.

Thank you mrwunrfl & lcuy. The travel days are listed in order and I've done a spreadsheet to calculate if the JR Pass is value for money for us and turns out it is. Just wondered if it was worth upgrading to Green but sounds like Ordinary will be just fine.

And yes mrwunrfl I keep looking at that trip from Takayama to Miyajima and wondering if it's really worth the effort?

Worth the effort? Well, you will settled into Japan somewhat by the time you make that trip. But, it depends on how long you would spend in Takayama and Miyajima and, to some extent, Gora. One night in Gora, one night in Takayama, one night on Miyajima would be crazy.

Gora to Takayama is a 6+ hour trip, so 2-night minimum there. But that would be tough, one free day between two long travel days, so you'd really want three nights there ...

I think you were wondering if going to Miyajima was worth it but you can ask the same about Takayama. There probably won't be any cherry blossoms in Takayama in early April. I saw buds there during the festival, about the 14th. Also, it was a bit cold and rainy.

But, back to your OP: consider that your use of green cars will basically be Odawara to Hiroshima to Kyoto. That would add up to a minimum of 6 but more likely 8 hours of actual butt-in-seat green car travel time. About 30 Aussie dollars per hour.

I thought that the Sanyo shinkansen trains didn't have green cars but that appears to not be the case.

Thanks mrwunrfl. It's our first time in Japan so we're pacing ourselves by having 3 nights each in Tokyo, Gora and Takayama to allow for the travel. Then it's a short stay in Miyajima before heading up to Naoshima and on to Kyoto. Fingers crossed it's not too wet and chilly!

To answer the OP's original question, it seems useful to actually describe the difference between the Green and Ordinary cars.

It's useful to know that there are many different seating configurations on Japanese trains. On many Shinkansens, green cars offer 2 + 2 seating while ordinary cars have 2 + 3. Also, the distance between seats is greater on green cars. Finally, green cars usually have a much higher % of empty seats than do ordinary cars.

In short, you have quite a bit more space on a green car than on an ordinary car. However, you still have a decent amount of space on ordinary cars (much more than, say, an economy seat on an airplane).

Whether or not it's worth it to you depends on your preferences and budget.