My criteria for good bindings are:
Even width
Binding is full
Well mitred corners
If using a patterned fabric then cut with the pattern and not grain line (length or cross) Or, referred to as fussy cutting the binding.
If using 2 1/2" cut binding makes the back too wide then cut the binding a little narrower. However, if the binding is wider on the back than the front, this is ok as long as the amount is even. I prefer to have the edge of the binding just cover the seam line on the back of the quilt. I usually sew with a 3/8" seam rather than a 1/4" seam unless the binding is on the edge of patchwork and must use the 1/4" seam.
These are the basic criteria we use in judging binding.