Yes, I see now that krici is defined as "x1 believes [regardless of evidence/proof].....". However, in English you can believe something even if you don't disregard evidence (which I feel the definition for krici suggests), for example if you don't have enough evidence to be completely sure about what is correct, but you can make an educated guess.
Example: "I believe the hammer is on the upper shelf."
You wouldn't say "I am of the opinion that the hammer is on the upper shelf." and I can't quite put into words why. It's just not something that you have an opinion about. For me, it feels the same way to say that "she was of the opinion that he was just pretending.".
Again, this might come from the very clear distinction between "tycka" (having an opinion) and "tro" (believing) in Swedish (my native language), where some things clearly are opinions and some are beliefs (for lack of a better word). I actually think that sruma and krica are quite close in meaning, regarding what goes on in the mind, and only different maybe in application on different kinds of thought. I would prefer sruma in this case.
I have to disagree with the definition of opinion as justified belief. I know you wrote "roughly", but I see opinion as something fundamentally different from a belief. It feels like a completely different mindset. I think I would say that you can only have an opinion about something which isn't either true or false, something where preference is applicable. And it doesn't have to be justified at all, it can just be a hunch, a feeling, as well as well thought
arguments. Please let me know if this is not how an opinion is defined in English!
Maybe this is a little bit OT, but I find the subject very interesting!
Cheers!