The first one would be the strongest in this case. The use of “une/un de ces” heavily relies on the “ces” part:

Vous m’avez fichu une de ces frousses !

Even though the translation for this one would be “You scared me to death”, it is much easier to explain the importance of “ces” with a more gross, literal translation: “You gave me one of those fears !”

“ces” and “those” translate the same feeling in this case: they mean that the “frousse” we’re talking about isn’t just a random “frousse”, but that it belongs to a certain category of “frousses”. Here, we are implying that it is, indeed, the strongest category of “frousses”.