That depends on the medium. lds.org, the iPhone, and iPad appear to be defaulting to Georgia. Most non-English copies of the Book of Mormon that use a Roman script appear to be set with Palatino. I don't know what typeface was used in printing the 1979 and 1981 LDS editions of the English standard works.
If I remember, English LDS Scriptures are created in Great Britain with a standard typeface of Oxford University Press, or a thing like that... I believe this font aren't available for download.