These models can be useful for following trends in your area, however, they very rarely provide accurate valuations for specific properties. Anyone who has done a search on zillow has noticed this. A quick Zillow search will yield properties with “Zestimates” hundreds of thousands of dollars above and below actual market value. NAR is developing a tool for home valuation based upon MLS data from all over the country. The problem is that not everyone has to participate. Any agent or homeowner can choose to opt out of this, thus substantially affecting the end result data. It only takes a few agents within a subdivision to opt out to throw off the data greatly.
In the end, rely upon your own research through the county records, as well as credible appraisers.