Your county recorded a class, a town, a lot size and — where it measured one — a building size for your property. This finds the parcels it recorded the same way, and shows what it assessed them.
Owners usually bring neighbours they know. The board asks why that house is comparable, and "it is on my street" is not an attribute the assessor recorded — so it cannot contradict the assessor.
Turn it around. If two parcels agree on everything the county wrote down and are assessed differently, the difference is unexplained by the record the assessment was built from. That is not a better comparable. It is a contradiction inside the assessor's own file, and you do not have to argue what your house is worth to point at it.
The most useful row is the one nobody can tell apart from yours. A larger gap against a looser match is easier to explain away and worse to lead with.