Depends on conditions - gusty nasty stuff and I teach crab, converting to wing down at about 50 feet - I tried teaching wing down all the way a few times in these conditions - but the student usually goes gaagaa due to cross controls and weird feelings of the slip. However, in a rare steady smooth crosswind I'll teach wing down - which seems to help later on with their last 50 feet during the more usual gusty stuff.
I don't think there is a right or wrong - some seem to like / cope with one or another technique - but I do think that its best to know how to do, and the limitations / benefits of each method.
As an aside, I'd be keen to compile a list of 'pithy'confidence-building phrases used by other instructors during the last few feet, when things get interesting!!!