Yamaguchi or Saga

Hi,

I am landing in Fukuoka and will be travelling to both Shimonoseki and also Nagasaki. I could not make up my mind if I could explore Yamaguchi(not going any further to Iwakuni)or Saga.

Anyone can advise in term of activities/sightseeing which area is preferred.

Thank you!

I've only been to Yamaguchi, but the combination of Hagi and Tsuwano (Shimane Prefecture) was good.
I also stopped by Akiyoshidai on the way.
https://www.japan-guide.com/list/e1239.html
https://www.japan-guide.com/e/e5875.html
I didn't go, but I think Rurikoji is also good.
https://www.japan-guide.com/e/e6100.html
I have never been to Saga, but I would like to visit Takeo Onsen. (Mifuneyama Rakuen, etc.)
https://www.japan-guide.com/list/e1241.html
https://www.mifuneyamarakuen.jp/
Decide what you like.
Also refer to this.
https://www.visit-jy.com/en/
http://www.saga-tripgenius.com/

I loved Hagi, and we had a couple of quiet but interesting days in Tsuwano. Both are well and truly off the beaten track, even for Japanese tourists. It's a lovely part of the country.

Enjoy your time in Japan!

Above all, One of the musts about Shimonoseki is Kanmon Tunnel Footpath (a 780-meter-long undersea tunnel for pedestrians). This is a kind of activity!

https://www.gururich-kitaq.com/en/spot/kanmon-pedestrian-tunnel

If I am expected to choose Yamaguchi or Saga, I will choose Yamaguchi,
because it has more variety of tourist spots, such as Akiyoshidai(unique karst formations and caves), Hagi and Tsuwano (old style towns), and Tsunoshima and its bridge(magnificent view).

However, as you know, Yamaguchi is quite opposite to Nagasaki, and trains and buses to travel around Yamaguchi are not so frequent.
If you choose Yamaguchi, it would be better to spare enough time.

Saga is neighboring Nagasaki, so you can find and visit more places than Yamaguchi.
Some of the famous areas are Arita and Imari (known for ceramic wares), Karatsu (Niji no Matsubara pine grove), and Genkai Sea (ria coasts).

I really like both of these prefectures. In addition to some of the sites others have mentioned in Yamaguchi, Hofu Tenmangu Shrine and Motosumi Inari Shrine. Yamaguchi City has some nice temples, too.

Not much has been said about Saga, but Saga is a great and highly underrated prefecture.
The sites listed by Japan-guide (this website) are good.
-Yutoku Inari Shrine is highly worthwhile. It's definitely among the most beautiful in Japan. Hizenhama Historic district is well-preserved, as well.
-Yoshinogari is a great historic site. It took a lot longer to explore than I expected.
-Arita's historic district is pretty.
-Okawachiyama is also a picturesque pottery town.
-Ureshino Onsen is a great onsen that has a noticeably great feeling on your skin. The only other onsen I know of like it is Ikeda Onsen in Gifu, so it's definitely unique.

Places not found on this site:
-In addition to Karatsu Castle, Nagoya Castle, etc. listed on this site (Japan-guide), the Former Takatori Residence in Karatsu is also worthwhile.

-The Takeo Onsen link here just talks about the onsen and the library, but it leaves out Mifuneyama Rakuen Garden and Keishuen Garden, both of which are worthwhile.

-Ouo Shrine has very famouss torii gates leading out in the water. It is popular for pictures, and the experience differs depending on the tide.

-Arita's Porcelain Park is very beautiful.

-In Saga City, Saga Castle is interesting and Furuyu Onsen is not well-known by foreigners. Kyoseki Park looks interesting, but I've not been there.

You can see more about Saga here:
https://en.wikivoyage.org/wiki/Saga_(prefecture)

Saga and Yamaguchi both have a lot of interesting sites, so there is no wrong choice.

Both are easy drive destinations for us in Fukuoka. Where to pick up depends on season.