Why proximity doesn't mean the same market
Windsor-Essex includes an actual city — Windsor — plus established, growing suburbs like LaSalle and Tecumseh, alongside smaller agricultural towns like Essex and Leamington. Chatham-Kent, by contrast, is organized around one larger city, Chatham, surrounded by a wide network of smaller towns and rural communities with generally more agricultural land and fewer large suburban subdivisions.
That structural difference matters for a buyer or seller — Windsor-Essex generally has more housing stock variety concentrated closer together, while Chatham-Kent's comparable sales for a specific small town can be thinner and more spread geographically.
What actually stays the same across the border between them
The core factors that price an individual house — roof, furnace, wiring, foundation — don't change crossing from one region into the other. A buyer who genuinely works both regions, as this one does, is pricing the same fundamentals; what changes is the comparable sales data and local context available to check that pricing against.
Why it's worth asking a buyer which region they actually know
A buyer unfamiliar with one region but experienced in the other can still price a house reasonably using the same fundamentals, but local context — what's typical for the town, what recent sales actually looked like nearby — adds real accuracy that a purely formula-based estimate misses. Worth asking directly rather than assuming regional experience is interchangeable.