a more square like wing (constant chord) has the lower wing loading, a more tapered wing rolls, snaps and spins better but when it is too much it tips stall, a more forward swept wing concentrate lift at the root, so, it has less tendency to tip stall but the model is less stable in flight (desirable for 3d, undesirable for pattern), finally a thick airfoil means a slower airplane and a sharp leading edge means it will have a stall at a lower AOA witch can be desirable for 3d (a stable harrier must have a full stalled wing)... uf! hope this helps

Daniel