[encoderer]

As far as number of listings of on-market homes, Zillow and Trulia are certainly very close to one another. Possibly in your local market that wasn't the case, but generally speaking it is.

At Trulia, we also calculate Estimates for properties but in most cases we do not show that data. In theory, the estimates work much the same way an appraisal works: Comparing the home on its various attributes to recent sold homes nearby. Obviously it's not possible to capture the essence of an Appraiser in an algorithm, but we display the estimates in cases where we feel it's better than just showing an old, out-dated last sale price.