[upofadown]

DC is generically more efficient for transmission than AC. That is why it is used for very long lines. It used to be that you needed to stay AC to use transformers to step up the voltage but those days are long past.

>Brushless DC motors actually require a separate circuit to turn DC into something resembling a sinusoidal current (i.e. AC).

Typical split phase AC induction motors used in residential applications are not very efficient and have various other deficiencies. There is a tendency to do a AC>DC>AC thing to a 3 phase these days for smaller electric motors and get variable speed as a bonus.

>...wind generates AC.

But not at any particular frequency. So typical wind turbines have a AC>DC>AC converter to allow them to sync up with the grid.