Comparable sales carry the most weight when there are several of them, adjusted for size, condition and lot, rather than a single favourable outlier presented as proof. 3 to 4 comparables weighed against the city's own data set carry far more weight than one.
A factual error is the cleanest kind of evidence, because it does not require an argument about value at all, only a correction: the wrong finished square footage, a bedroom that does not exist, or a secondary suite classified incorrectly on the roll.
Sentiment about the bill being unfair does not move a hearing; a stack of comparable sales and an accurate property record does. Get your hand-reviewed valuation from Joel Dyck.