What sort of answer are you looking for? Do you want an answer that convinces you? Do you want an answer that lets you trump a committed atheist is just wants to argue (do you just want to argue and ‘win’ or do you actually want to convince)? Do you want an argument for someone who is honestly questioning, feels pulled towards the something and doesn’t know whether that thing is the Catholic Church or not? Or is this in answer to a loud Protestant calling you an idolator?
An interesting question might be, honestly, why do you think the Church has the truth? Is it because you were told that by your parents and never questioned it? Is it because you felt the pull and just decided to accept what you think the Holy Spirit was telling you? Or was it some great apologetics argument?
The thing about philosophy generally and apologetics specifically is that different sorts of argument make sense to different people at different points in their lives. An argument that seems like a slam dunk to you now may seem just silly to you ten years later.
Likewise, if you’re arguing with someone in bad faith, really just ‘debating’, you aren’t going to convince anyone. And, frankly, by looking at the diversity of opinions on the matter, there isn’t a slam dunk argument that going to convince everyone. I mean, 50% of people raised Catholic leave the Church in the United States. Clearly, they’re not convinced.
The best you can hope for if what you want is something other than to argue well is, if you’re having the discussion with someone who is really open, listen to them, really listen, and see where they’re open to consider new ideas. For some people, it might be the historical arguments for Apostolic Succession. For others, it may be the weight of the Catholic intellectual tradition. For some, quoting Scripture about Peter being the Rock will resonate. A good Protestant will just quote Scripture right back at you and, being a good Protestant, probably knows their Scripture a lot better than a Catholic does and you won’t win.
In other words, it completely depends on who you’re talking to and what they’re open to.