I’ll try to keep this brief and limited to when I was looking into Catholicism, not ways that I came closer to Catholicism while a Presbyterian (compared to my mostly Pentecostal and Baptist background). Also bear in mind, I’m coming from a Protestant background, so that’s what I’ll focus on.
First, there’s the issue of the canon. We rely on it to know what Scripture is, but nothing in Scripture declares what that canon is. (I’ll ignore the circular reasoning argument, since it did little for me when I was searching.) This leaves us with a dilemma. We could say that God, through extra-Scriptural means, gave us the canon, but then we no longer hold to
sola scriptura. Alternatively, we could take the R.C. Sproul of approach of a “fallible collection of infallible books”, but then we’re left with relying on a Scripture we access through a fallible source (i.e. the Bible), which seems like a foundation of sand.
Second, and further down
sola scriptura, there’s the issue that it isn’t itself Scriptural. The doctrine at its most basic is that Scripture is alone God’s revelation of His teaching to us. Nowhere is this taught in that very Scripture. Scripture teaches that it is infallible, but Catholics accept that. Scripture teaches us that it is sufficient, but that’s not a reason to believe that it is alone infallible, as St. Vincent of Lerins pointed out in
Commonitory 2:5. Basically, it is self-defeating doctrine.
Third, there’s the matter of justification. We have numerous examples in Scripture where works like baptism (1 Peter 3:21), partaking the Eucharist (John 6:54-56), and works of charity (Matthew 25:31-46) play a role in justification. Of course, James 2:24 explicitly states that works play a role. While God’s grace is free, there’s clearly some work of cooperation on our part to accept it, something God Himself empowers us to do. While Romans and Galatians do criticize works, it’s clear from their context that Paul was dealing with the Judaizers, who you can read more about in Acts 14-15. This is very clear in Galatians 5:6, where Paul makes a very clear separation between circumcision (again, Judaizers) and charity.
Finally (for this post, certainly not all), there was the general call among many early Church fathers to unite with the Bishop of Rome. Sure, there were political reasons to keep Rome as a the center or favor it over other churches Peter established, but it’s no secret that that bishop is of the line of Peter and was given a primacy in the early Church.
Again, those are just a few things that pulled me away from Protestantism and into Catholicism. There are a lot more, but I think I’m already approaching the character limit.