There is a slight structural advantage to a tapered stabilizer, It moves the center of pressure closer to the fuselage reducing the bending moment at the root, and since the thickness is usually tapered as well as the chord (at least on full scale aircraft) the structure is more efficient. Aerodynamically it makes little difference if the trailing edge is swept forward like the Mooney or the leading edge is swept aft like on most or even if both leading and trailing edges are swept and the spar is straight. Like much in airplane design it is a compromise between the stubby tapered planform which is structurally more efficient and a wide span narrow chord planform that is aerodynamically more efficient.