Because expert selection presents stones which do not fit into the branded ACA checklist, they can be looked at as stones which present the best value for the money . A good idea is too check out the Ideal-Scope images for these stones and not just the optical symmetry of the arrow shafts or patterning, so you can get a good idea of light return for stones which have a broad range of proportions.
I think the most important point to consider is picking out a beautiful diamond at a good price.