I think you should be careful with prospective convert so you are not seducing him into your favorite minhag, as if your synagogue is the holy one; and that other shul is not so good; unless you are really sure of this minhag then you should be careful to warn him. @SpiderJerusalem: Its good to know that people who call themselves Haredim really follow passul minhag because an outsider might think they are kosher.
I would warn someone who was interested in being mgayer to my minhag: “I pretend to follow the righteousness of my forefathers which I’ve inherited from them; but frankly I am not so righteous as the earlier generations; because well, this religion is really hard and I’m lazy. You would get closer to haShem by going elsewhere.”