Speaking of the GSEs AVM, the quality of the data they have access to greatly exceeds the amount of info in the data used by every commercial AVM. They have access to actual appraisals which have been performed at one time or another on most of those properties. Often including the subject AND some or all of the comparable sales. Sometimes including the appraisals actually used for those specific transactions, other times being limited to prior appraisals.
If a property has 1 or 2 prior sales in their sales history and 2 or 3 or 5 previous refis then the GSEs most likely have at least one prior appraisal on file for that subject. So they're not 100% dependent upon an MLS entry or public records entry as is the case for the commercial AVMs. The weak spot in all AVMs is their use of unverified property attributes; it always has been. The GSE-archived appraisals solve that problem for them insofar as the properties that have already been through their pipeline in the past. That won't be all the properties that get used for comps but it will be most of them.
So the comparison here isn't between what a 1004 appraiser knows about a property vs what Zillow or Corelogic knows. The comparison is (at least potentially) between everything the other AVMs have access to + everything the GSE has previously extracted from the appraisers on that subject and on most or all of the comparables used in the appraisal.,
