Another item that I think your consultant missed in his list of items in Old Search that are not in New Search is that the search templates for Old Search often include searchable fields that are not listed in the search templates for New Search. These searchable fields that are missing in the New Search templates vary from database to database.
For example, the U.S. Public Records Index databases have a searchable field for the person's address. This field is present in the search template for Old Search but not for New Search. Such data seems to be searchable in New Search as keywords, at least some of the time. But searching for this data as keywords does not always produce the same results as Old Search or results that are as good as Old Search. Of almost more importance, searching by keywords is sort of a big black hole. You have no idea what kinds of things are searchable as keywords. With the Old Search templates, you could tell what was searchable.
This whole problem with the search templates for New Search came about because of the desire on ancestry's part to automate the production of the search templates and thereby to reduce the burden of search template maintenance. But automating the production of the search templates caused the loss of a lot of very useful functionality for the users.