Socia River( Kobarid) vs Logar valley

It depends what you are interested in. Hiking? History of WW I? 4 nights - ie. three full days - in each location? We enjoyed northern Slovenia a lot but three or four days rather than two total would still have been fine. Unless we wanted to do some serious hiking, Great area. Have fun!

On a 25-day trek through Slovenia n 2019, I did 4 nights in the Logar Valley and 3 nights in the Kobarid area. My trip report that includes an overview of the itinerary before diving deeper into a variety of topics: https://community.ricksteves.com/travel-forum/trip-reports/25-days-in-slovenia

We were in Slovenia last month, spent three nights at both of these places. Here is our report:
https://community.ricksteves.com/travel-forum/trip-reports/slovenia-14-days-13-nights-road-trip

Thanks everyone, very helpful ideas.

Another question...We are renting a car in Ljubiana and will be driving to Lake Bohinj and I would like to avoid the long tunnel on the fast road! Is that possible?? I hate long tunnels
Thanks again

If you must avoid tunnels, you can use google map to find alternate ways, but the detour might be long. I don't remember any "long tunnels", there are some tunnels here and there, they are well maintained and brief.

I also do not recall any long tunnels. There is a forum member who promotes doing a scenic drive on two-lane highways that goes through Škofja Loka and on to Bled. He reports it is a beautiful drive. I don't know the tunnel status of that road. You may use the search bar to see if you can find what he has written about that drive.

I just drove between Ljubljana and Kranjska Gora. There are definitely no long tunnels on that route, which is a couple of exits longer than the Bled one (you pass thru Bled to get to Bohinj). On the other hand, I do recall a longish tunnel on the way to Logar valley. But it was very well maintained and well lit, so no cause for concern. The highways were a pleasure to drive on and well maintained.