Sharp betting exchanges like Betfair and Smarkets trade huge volume and price events faster and more accurately than Polymarket. You strip out their built-in margin (the 'vig') to get their true implied probability, then trade Polymarket whenever its price still lags the exchange's line on the same event. The edge is pure information leakage: the deeper, faster market moves first and Polymarket's order book catches up slowly.
Markets on Polymarket where betting-exchange volume & vig leakage is the natural play:
