According to Calvinism, if Catholicism might lead to salvation, why to remain a Calvinist? (Henry IV story) In his 1786 book, &quot;The History of Heresies and Their Refutation&quot;, (saint) Alphonsus Liguiri wrote:

I think the danger of eternal perdition, by dying separated from the Church, should be a sufficient motive to convert every heretic. It was this that made Henry IV [of France] forsake Calvinism, and become a Catholic. He assembled a conference of Catholics and Calvinists, and after listening for a time to their arguments, he asked the Calvinistic doctors if it was possible a person could be saved in the Catholic faith; they answered that it was; &quot;Then,&quot; said the King, &quot;if the faith of the Roman Church secures salvation, and the Reformed faith is at least doubtful, I will take the safe side and become a Catholic.&quot; (p.634-5)

The logic in the above story is simple: If Catholicism is true, Calvinism leads to perdition; If Calvinism is true, Catholicism might lead to salvation. Ergo, statistically speaking, it is more convenient for salvation to be Catholic.

Naturally, the above is valid if and only if:
1. According to Catholicism, Calvinism leads to perdition:
In my understanding of this, before the Second Vatican Council, the interpretation of the phrase &quot;there is no salvation outside the Church&quot; (Extra Ecclesiam nulla salus) was that non-Catholic Christians could not be saved. This is surely in line with the argument of the story, and what Alphonsus believed. However, after the Second Vatican Council, and without a change in the dogma itself, the interpretation of the phrase allows for non-Catholics (e.g Calvinists) to be saved. In this sense, the argument of Henry IV, from a Catholic perspective, falls apart.
2. According to Calvinism, Catholicism might lead to salvation:
As I read online, the key doctrine about salvation in Calvinism is that of predestination. Besides the seemingly divergent understandings of what this means, at least from what I read, predestination is surely open to Catholics. Or, to say the same, it is not closed to them merely because of being Catholic. In this sense, the &quot;Calvinistic doctors&quot; of the story were right.
Please indicate in the answer if this is not the case (i.e. that according to Calvinism there is no salvation in the Catholic Church).

If point 2 above is correct, then it is just natural to ask: would it be more sensible for Calvinists, from a probabilistic sense, to adopt Catholicism as their faith, just as Henry IV &quot;did?&quot; Or, to put it differently, what is the counterargument in the above story? Why is it sensible from a salvific point of view to remain a Calvinist?
PS: a quick glance at Wikipedia suggests the story of Henry IV might not be true. But that's beside the point.
The Calvinist answer to the question "is there salvation in the Catholic Church" is "yes and no." It is "no" because there is nothing salvific in being affiliated with the papacy. We deny the legitimacy of the office of pope, in addition to many other unbiblical offices and deny sacerdotalism entirely as a scheme of salvation. A person whose hope for a basis of salvation is placed in the pronouncements or presumed dispensation of grace at the discretion of Roman Catholic priests is someone a Calvinist would consider unsaved or at least very confused and saved in spite of it. 

The "yes" part of the question is based on the belief that salvation is found in Jesus alone and it is fully possible to be a member of a corrupt church and yet be a sincere believer. 

The idea that a person would be a Catholic "just to be safe" would imply that they are not trusting in Christ for forgiveness but rather in their church membership or placing their hope in men. The Calvinist position is that salvation is by direct faith in Jesus Christ alone, not faith plus works, nor faith plus membership/blessing by a priest. We don't recognize apostolic succession as a legitimate biblical concept except in the succession of apostolic doctrine. 

Reformed confessional documents rarely even offer the name "Roman Catholic" as a courtesy, preferring names like "papcy" and "papist" due to a lack of desire to grant the premise that "Catholicism" is "catholic" (i. e. the universal church). The Westminster Confession of Faith in the chapter on marriage forbids marriage with "papists and other idolators" (chapter 24).

The default posture of Calvinism towards Rome is to view them as a mission field in the form of a true church that has been corrupt (hence we recognize Roman baptisms as legitimate baptisms whereas the baptisms of heretical churches like LDS or Jahovah's Witnesses we would not recognize and would judge that the person would need to be baptized for the first time).