As usual-it depends.
Sometimes using a boundary mic is a nightmare.
Sometimes they get covered up by a Bible, notes, banners etc.
If the talker is flipping pages in a Bible, this can get quite loud.
A boundary mic is good for wide area pickup and less fluctuation of levels, but I have found as a general rule, a condenser on a goodneck is the best way.
Depending on how much the people move around, an omni may be a better choice-or not.
Some people like to stand beside the pulpit and talk. A regular cardioid is not a good choice in this case.