You choose. It is like selecting a house to buy. What is best for me might not be best for you. Some people like maximum profit. Some people like to win most of the time. I like to see trading methods and security price histories that show a wide range of profitability regardless of the parameters used. Some people might prefer to minimize volatility. If I was attempting to minimize volatility then I might examine the standard deviation of profits and losses of all simulated trades. You might want to study Sharpe Ratio, Calmar Ratio, Sterling Ratio, and Traynor Ratio. There are probably other measurements of system performance also.