I actually prefer to play and sing it in 6/8, or at least at a faster tempo than is usually used in churches.   Partly because you don't need as much lung capacity that way, but partly because I just think it sounds better.

The site leeneia linked to has 3 different nice MIDIs, but they all have the tune that's attributed to Franz Grüber and which story he seems to be corroborating, above. (I wonder if at the time and place, it was considered proper to write about oneself in the 3rd person in documents such as that).
Their "Pronunciation Guide" leaves a lot to be desired, IMO, but it's a very useful site.

Satz für Orgel von Franz Xaver Gruber, 1855 Dank Bill Egan
Satz von Joseph Mohr ~1820, die frühest bekannte Melodie Thanks to Bill Egan*
Melodie - Melodie - Nach Franz Xaver Gruber, 1818 (1787-1865)

*Same tune as the other two, just a slightly different instrumental arrangement