I really think the main factor in determining if prediction markets are valuable is their predictions from outside election day. Once the “blue tsunami” was “expected” most of the markets shot overwhelmingly in one direction as the night wrapped up. You need to have a boundary for comparison that isn’t influenced by election night. Starting at 5AM is a decent cut point but I would argue the final poll date is the best comparison.
Love or hate PolyMarket, it should be on this list too.