The difference shows up most on a home with unpermitted or undocumented work. An online estimate or a generic comparative market analysis pulls square footage, lot size and the last sale price from the public file, and it has no way to know about a finished basement, a new furnace or a renovated kitchen that was never inspected or reassessed.
Joel's process starts with a walkthrough rather than a desktop report, so every improvement gets recorded before a number goes on the listing. That matters most for sellers working against a deadline, since a valuation built on the wrong starting point costs time in price corrections later, not less of it.
For a seller who needs the sale to fund what comes next, that accuracy at the start is the whole point. Get your hand-reviewed valuation from Joel Dyck.