FFF and Fullwings,
Why do you mention that most crab landings are actually a combination of both crab and wing down methods. This is not true. As you straighten up using rudder you also use opp aileron into wind, however you touch down with both main wheels and with the wings level.
The main disadvantage of the wing down method is that the pax will be uncomfortable during the approach, leaning over to one side seems crazy to me.
Crosswind take offs are more limiting and demanding anyway, although most people thing the landing is the most difficult.
its not.