Several methods have been adopted by different researchers to test for isomorphism in Planetary Gear Trains (PGT) and out of these isomorphic PGTs, one PGT is selected at random. There is no definite basis for selecting a particular PGT out of the isomorphic graphics for further generation process. Structural aspects and rating of the PGTs are useful in selecting one such PGT for further generation. Symmetry in PGTs is one such aspect. PGTs with symmetry generate more possible higher level graphs than PGTs with no symmetry.