Iya Valley or Kiso Valley?

Hello !

I will be travelling to Japan from late April to mid-May this year, and would like to spend a couple of days hiking in mountainous/hilly areas.
I am really interested in visiting both the Iya Valley in Shikoku, and the Kiso Valley in Nagano/Gifu prefectures. However I probably won't have enough time to explore both. Therefore I would be happy to have advice from people who have been to either one of those places (or both ?) and their recommandation : what did you like there, how easy it is to access (I won't be renting a car but I have a JR Pass and a pretty light backpack),did you find cheap accomodation, how hard the trail was, etc.... Anything that could help me make a choice between the two valleys :)

Thanks in advance, and have a good day !

Odile

I have visited both: Iya Valley for beautiful onsen; Kiso Valley, mainly for the Magome- Tsumago uneventful hike.
Iya Valley is harder to reach with public transport. Buses and trains are infrequent, a rental car is the best option for the region.

Kiso Valley is more touristic, but has also more attractions like Edo-merchant streets. Iso Valley is more focused on nature only (with exceptions of those famous brides), so Iso feels more remote somehow.