Somehow my brain does'nt like the idea of mostly the rudder or elevator turning the plane in a rolling circle, dependent on the direction of the turn. If thats the case, your doing a really bad slow roll, in either direction The plane cant care what way its rolling, the rudder being the predominant yawing control while the wings pass through the horizontal position, and the elevator while the wing passes through the vertical position.

I rather think its just a head game. You could be feeling the planes pitch and roll coupling making it seem easyer in one direction. Try doing plain knife edge circles in both directions, If the plane is truly neutral, the rudder and elevator input should be the same, but opposite in direction. Of course, few planes fly this neutral. JMO

Kevin