Rockazella, The most efficient wing planform (all else being equal) is an ellipse, like the supermarine spitfire. This is because an elliptical lift distribution across the span results in minimum induced drag for a finite span wing. The elliptical planform is hard to construct and a tapered wing is almost the same, especially if the tips are rounded. This is why most full scale aircraft have either a single tapered wing (like the Mooney) or a combination of straight center section with tapered tips (like the many cessna models). I own and fly a Piper Cherokee which has the rectangular ("hershey bar") wing and also have considerable time flying the Piper Archer, which is essentially the same aircraft with a tapered outboard wing section. At lower altitudes the difference is not a lot, but at higher altitudes, the efficiency of the Archer is obvious. The efficiency shows up as a better rate of climb at equal power settings, a higher service ceiling, and increased cruise range.

Our radio controlled models are so grossly over powered that the difference in efficiency would probably never be noticed, but it is there.

Generally a thicker wing section will operate at a higher angle of attack before stalling. Since the tightest radius of turn occurs when operating at maximum lift coeficient (max angle of attack) the higher the angle of attack a wing can achieve before stalling, the more "maneuverable" it will be. As matter of fact, if the wing is given a little camber (so called semi-symetrical, or even the old flat bottom type) it will turn even tighter. However when performing inverted or negative maneuvers, it would stall at a lower angle and would not turn as tight. It is this requirement for inverted flight, and negative g maneuvers that dictate a symetrical airfoil for aerobatic aircraft.

I looked up the xfoil site and find it interesting. However the design of an actual wing involves a lot of tradeoffs and compromises in addition to airfoil section. In spite of an AE degree and many years experience in the field, when I sit down to design a model I still use a lot of TLAR. If you are interested I can send you pictures of my latest designed from scratch models. If you want to pursue the technical route a little more you might check the library for "Principles of Aerodynamics" by James H. Dwinnell, and "Airplane Performance Stability and Control" by Courtland D Perkins and Robert E Hage.

I hope this helps. Keep us posted.