The answer depends on a lot of things. If you typically use more than 5 degrees of aileron deflection in a turn then you can expect to have flow seperation on the bottom surface of the up-going aileron and a sharp increase in profile drag. Also, the up-going aileron reduces the average lift coefficient of the wing making high G turns wider for a given angle of bank than with two ailerons or one down-going aileron.

My guess is that if you normally turn with less than five degrees of aileron deflection, you shuld stick with your present arrangement. If you normally use more than about 5 degrees of deflection, you would be better off with two ailerons and less deflection.

The 5 degree criterion is based on a thin airfoil with very smooth and slightly rounded contour to the hinge line with a seal and minimum gap. If your hinge line isn't very smooth and virtually gap free, then about 3 degrees of deflection will probably produce flow seperation and a sharp increase in profile drag. Obviously, the up-going aileron should be hinged on the bottom surface and the down-going aileron on the top surface to minimize flow seperation in high speed turns. From a flow seperation point of view, skin hinges are best, tape hinges next best and pinned hinges are worst.