The case that it is preferable to mine real estate records is made in The Pennsylvania Magazine of History and Biography:
Genealogists seem to neglect the real estate records that are so carefully preserved in the court house of every county throughout the country and should be reminded of the large amount of family history they contain.
It has been the writer's experience that these records give much better genealogical data than do wills for the tracing of ancestors and relatives. Wills when found do not always give good results. Present day wills devise at least a small amount to every heir, but the old ones did not do so and frequently one or more of the heirs were not even mentioned in the will. The relationship between the legatees and the devisor was seldom stated clearly. As a consequence brothers and nephews may be mistaken for sons, sisters-in-law and daughters-in-law may be mistaken for unmarried daughters, married daughters may be unidentifiable, and mere friends or servants may be mistaken for married daughters or sons-in-law.