*edit* Sorry, forgot this was 'Ask a gamemaster'. Ill try not to post in here again
The difference is both mechanical and RPMechanically, sacred fists can't wield any weapons, having "creature" weapons, and get a few different feats (including uncanny dodge, which monks wish they had...)
Ah thanks for the clarification. Seems like a class that should be on the black list for Dorandites.
Mechanically speaking: Sacred Fists are missing a lot of the free goodies that come with being a Monk, but they can cast spells and they get bonus spells at every even numbered level as if they had gained a level as a Cleric (or Paladin...).