Wind turbine generator: brushed or brushless DC motor?
A brushed motor has the rectifier built in via the commutator.  So you don't need the 3 phase rectifier.  However, the brushes and commutator contacts do wear out and the brushes need to be replaced from time to time.  There are still losses associated with the commutator, even though not as much as with a diode bridge.  In a wind turbine I would think that maintenance could be painful so you would want to minimize it as much as possible.

The brushless motor is typically much more reliable and doesn't require periodic replacement of anything.  Depending on the output voltage (Speed and back EMF constant) the rectifier losses could be significant.  You could use a 3 phase FET bridge instead of a diode rectifier, but that becomes much more complicated.