Discrepancy

I would say the first sentence
In case of a discrepancy between the French version and the English version, the latter shall prevail.

The second sentence is just wrong -- I wouldn't try to say it that way.

I might try to say something like:
The English text is considered to be the official version.

But I don't know the context. Is this a contract of some kind? I think there is a proper legal way to say this that has been vetted by lawyers.

I think the first sentence is very clear and probably sufficient.

Hi Ebrown,

What the second sentence wanted to express is exactly the same as what the first one wanted to do.

I felt that you have very properly added the definite articles there. I just didn't get the usage of indefinite article. Because if there were two or more discrepancies there, the "a" might fail to help.