Does GIA Excellent Symmetry or “Hearts and Arrows” guarantee a beautiful diamond?
A look through the Ideal-Scope will show you a lot.

The stone on the left has better symmetry. However, the stone on the right has the better light return.
Excellent symmetry does not equate to better performance, but Excellent symmetry usually costs an extra 5% or more.
The diamond above is an example of an AGS 0 H&A’s diamond that would look
considerably smaller because of the leakage in the upper girdle facets.
Here are two non Hearts and Arrows diamonds with Excellent light return
Light return is the bricks and mortar, hearts and arrows is just a coat of paint