I'm not a theorist but yaw/roll coupling is very noticeable in gliders which have long thin wings that aren't blanked much by the long thin fuselage, so I would go with the one wing going faster than the other scenario. Seems to make intuitive sense.
Edit: I'm pretty sure that some radio controlled gliders don't even have ailerons, they just use the rudder for roll control. It's easily doable in a full size one.
Last edited by thing; 25th Sep 2013 at 11:36.