I considered that issue, but I figured that your propensity to oppose the freedom revoked in Scenario A would be directly dependent on your answer to this question.
For all intents and purposes, take it at face value as you are simply happier in Scenario A than Scenario B. Let's say, with or without the illusion if it's still an important matter for you.


If you have B, you have A
How does B exclude A's benefits while increasing options over A? Does B leave me free to leave B? Dont know, not enough info.
There is no freedom in scenario 1, thus scenario 2 has a limitless potential.
the best choice and the best possible outcome is notably worse than in Scenario A
You said:
So this boils down to the question if there is some sort of universal value in 'freedom' that makes it worth being miserable to have.
No there isn't, the whole concept is absurd.
The devil you know is better than the one you don't. The potential you refers to can be the potential for total disaster(Russia for example).
It is if you take it at face value, but a society as restrictive as scenario A is doomed to failure, human nature suggests the world favours freedom of choice, speech and belief to some significant extent. Governments which don't have this tend to fail or be in transition to democracy.
If you take it at face value, yes I suppose you would go for scenario A, but scenario A does not exist in a vacuum in reality and could never exist. So I'd say that it's either a pointlessly theoretical question, or if it has some practical aspect answer B is the more likely to be favoured in the long term.
Since I can't answer A as it's absurd, B is the only answer I can give that has any baring on the real world.
Scenario A has been the global de facto rule before the 1950's.
A has existed before. And I do not agree that something that makes you miserable will be favoured, especially not in the long term. There is no value in freedom except for what we put there and in this scenario it is stated that it is not highly valued.
Why is being happy without having endless choises absurd?

There is no freedom in scenario 1, thus scenario 2 has a limitless potential.
B with more freedoms, more people on average would be happy, so to sacrifice some of my happiness for the whole would be no great hardship. Given the choice I'd rather live in Venezuela than in Cuba.
It doesn't say it makes you miserable just that you wont be as happy as A.
I think the point is clear, A is unlikely to exist for any great period of time in the modern world. Thus it is absurd to place the precondition that B will not turn out better than A, because reality shows otherwise.
If having more freedom makes people unhappier than being very restricted then the experiments preconditions are also flawed as that is seldom the case.
I'd show you the happiest countries in the world, from Scientific American, but its buried in the Archives and I don't have a subscription. Suffice to say the top 30 are almost all democracies, although worryingly the US only just slipped in at no 28 and was beaten by India IIRC.
Britain was third, Ireland was 1st according to the study. Criteria was happiness with government ( article was pre Bush Jr under Bill Clinton, or very early Bush I forget which) happiness in general, economic happiness, and various other political considerations and social implications. 1000 people from all walks of life and every socio- economic class were polled. Fact is freedom is an essential part of happiness. Have you noticed the bonuses you get with it in CIV, that's not a coincidence, free speech, free religion, representation.
It depends how notable "notable" is, obviously. I value freedom sufficiently that I would sacrifice other things that make me happy to attain a certain level of freedom.
NB:
1) The implication is that freedom also makes me happy. If in Scenario B, when you use the word "happiness", you have already taken into account the fact that freedom makes me happy, and that level of happiness still falls lower than in Scenario A, then obviously I would choose A. But I took "happiness" to exclude the part of happiness that is derived from being free.
2) The other implication is that freedom vs happiness is not a linear function, and tails off. So the small amount of freedom in Situation A may be worth more than the additional (large) amount of freedom in Situation B.
What you mean in China and Russia?
It doesn't say it makes you miserable just that you wont be as happy as A.
I think the point is clear, A is unlikely to exist for any great period of time in the modern world. Thus it is absurd to place the precondition that B will not turn out better than A, because reality shows otherwise.

I'd rather have the freedom to make my own choices, then to be restricted to someone(s) elses designed lifestyle. Besides, there's only a devil if it's implemented into scenario 1, as it surely woudn't be in my own scenario 2 -- case & point, ftw.