In 1940 U.S. Census Index Comparisons - Post 2: Carringer in California, I displayed my comparison tables and found that Ancestry had 8 more Carringer entries than FamilySearch, and my judgment was that Ancestry was more correct on 7 of them, and FamilySearch for one..
In 1940 U.S. Census Index Comparisons - Post 3: Seaver in California, Part 1, Part 2 and Part 3 I displayed my comparison tables for Seaver entries in California, and found that FamilySearch had 22 more entries (147 entries) than Ancestry.com (125 entries). I analyzed all of the Ancestry unique entries, plus the ones that disagreed but were indexed by name correctly. My judgment for accuracy tally in these posts was: Ancestry = 13, FamilySearch = 29, Both wrong = 4, No decision = 7.
I want to move on to another surname in California - McKnew. This is my wife's great-grandparents surname, and her grandmother's maiden name, and I think this study may be interesting because of the "Mc" prefix to this surname.
Here is the top of Table 1 for this group:
There were 12 entries for an exact search for "McKnew" in California on Ancestry.com, and all of them were indexed the same way by FamilySearch. However, there were 23 total entries on FamilySearch. Here is Table 2that lists the six family units that were indexed as "McKnew" on FamilySearch but not on Ancestry:
The discussion on each of these is: