To be honest, I never looked into Old Bear but your question got me wondering so I went to YouTube and found a somewhat rambling but informative comparison between OB and the Opinel. The difference of note for me is that OB is sharpened on one side only and is made of 420HC. The Opinel is beveled on both sides and is out of the box sharper - being made of 12C27 which I guess most feel should hold an edge better under heavier (cutting cardboard, etc) use. So, I guess it might get down to intended use, ease of resharpening, etc.
The differences in the locking mechanisms also stands out and I wonder if the tab on the OB might end up rubbing against the leg if carried in a pocket. Of course, in a backpack, it wouldn't matter.
In the video, I liked the overall appearance of the OB better and probably would opt for the Olive wood if I made a purchase based on looks.
But if the deciding factor was a lasting edge under harder circumstances (even slicing salami, which would be important to me), I think I'd go with the Opinel.
Anyway, that's my 2 cents worth and I'm sure you'll enjoy which ever one you choose.
OG