There are soooo many things, it is almost impossible to know where to start.
I am a semi convert (if thats possible), in as much as I was baptized Catholic as an infant, but never catechized.
My grandfather was a Presbyterian minister, and I have attended a variety of chuches at different times in my life. Pick one, and I’ve probably been to at least one worship service.
In addition to the things that have already been stated, like the Eucharist, tradition, history, universality, for me, it had to be the “straight forwardness”.
When I went through RCIA, I was the guy in the middle of the class, that always had a question, or statement, or experience that would prove the Catholic Church wrong. Unforturnately, or actually fortuantely in my case, it was me that was proven wrong.
That’s awesome!